# Rainwater from a butt - de-oxygenated?



## Dr Mike Oxgreen (16 Apr 2016)

When doing my 50% water change, I use 9 litres of rainwater from my water butt, mixed with 3 litres of unsoftened tap water. This gives me roughly the 3° KH and 6° GH that I'm after, and I can tweak the GH up a bit by adding MgSO₄ solution if necessary. I use Seachem Prime as my dechlorinator, and use a full-tank dose (only 0.5ml for my ~20 litre tank, so it would be impossible to measure any less). I boil a litre or so of the rainwater to bring the new water up to temperature.

I often notice that the gill rate of my Otocinclus has risen dramatically after a water change, and this seemed particularly bad yesterday. They were also very restless, and the chili rasboras were nervous as well - schooling very tightly and patrolling the tank rapidly. Most of the blue cherry shrimps seemed fine, but I did see one swimming very erratically and seeming to have difficulty staying upright. There also seemed to be a migration of snails heading up the glass towards the surface, within half an hour of the water change.

I decided that there might be a problem with lack of oxygen in the new water, although I must admit that none of the fish were gasping at the surface. To combat this, I added 15ml of 3% Hydrogen peroxide in the hope that it would provide some emergency oxygenation. (Actually it may have been after this that I saw the shrimp swimming erratically, not sure). After this, the chilies seemed to calm down slightly over the course of the next hour or so, and perhaps the Otos' gill rate slowed very slightly although still too fast.

So, does anyone know the typical oxygen content of rainwater that has been sitting in a water butt for a few weeks? I can't decide whether it's likely to be de-oxygenated or not. I am drawing water from the bottom of the butt.

Is there any point trying an oxygen test kit?

I can't think of any other contamination: the water butt is plastic, as is the house guttering. The roof tiles are old, so shouldn't be leaching anything into the water any more. The bucket and jug that I use are not used for anything else. That said, I don't know if it's my imagination but the tank didn't look quite as sparkly clear just after the water change - but that could be normal.

The tank looks okay this morning although I haven't yet done a head count.

Any thoughts? Would low O₂ level cause rapid gill movement in one species, but 'stressed' behaviour in another species, without any gasping at the surface?


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## Dr Mike Oxgreen (16 Apr 2016)

Just a thought...

The Epsom salt I'm using is a normal gardening product. I keep a stock solution with 44g dissolved into a litre, and dose 1ml of this stock solution per litre of tank water to raise GH by 1°. Yesterday I dosed 10ml into the new water to give a small increase (otherwise I find the GH reduces over time, perhaps as plants are using the dissolved salts), and tested the tank water after the change: 3° KH and 6° GH, which is exactly what I aim for.

Any problem with this? Could there be something else in the product that I don't know about? Maybe I'll try an ammonia test on my stock solution to be sure.

The data sheet for the product says it's only MgSO₄ heptahydrate, so shouldn't be an issue.


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## Dr Mike Oxgreen (16 Apr 2016)

Just tested the MgSO₄ solution, and it's negative for ammonia, as expected.


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## xim (16 Apr 2016)

Years ago, my brother did a 100% water change using water that had been kept very long in a water butt. All fish died. Yeah I also think it was from lacking of oxygen. And Prime just worsens the problem as it also reduces oxygen level.


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## sciencefiction (16 Apr 2016)

Test the water in the water butt for ammonia and nitrite. Containers with stale water do go through nitrogen cycle.
Also, it's not a good idea to rely on matching the individual parameters when mixing water. Get a cheapTDS meter and mix the water to match a chosen reading, regardless of the individual readings of GH or KH. It's less risky on the fish that way.


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## Dr Mike Oxgreen (16 Apr 2016)

I do have a TDS meter, and use that to verify that the new water is about the same as the tank. It's within 10-20, with the tank measuring about 130.

The rainwater tests negative for NH₃/NH₄⁺, NO₂⁻ and NO₃⁻.

For my next water change I'll try mixing the water the day before and leave an air pump running overnight.


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## rebel (16 Apr 2016)

Good ideation try and oxeye mate the water first. Make sure add prime etc at the same rate.


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## sciencefiction (16 Apr 2016)

I wouldn't think the rainwater's oxygen content is the problem because in order for it to cause stress it means the remaining 50% of water in your tank is severely low on oxygen and it's easily tipped by the new water. An airstone or heavy surface agitation should fix that within 30min or so if that's the case. No need for hydrogen peroxide...

 What is the KH, TDS of the tank water at the end of the week, just before you pour the new one? My guess is you are swinging the stats or there's something "fishy" in the rain water. It's pretty uncommon for TDS to remain the same after a week of no water change so to what TDS are you matching the new one? The Kh gets lower over time too but if you are doing 50% water change weekly it should remain solid stable at  3° KH. It's a small tank so it's easy get it wrong if you are adding rainwater.

 Ottos can breathe from the surface and if oxygen is the issue, they'll be the least stressed ones in the tank, plus they'll shoot to the surface to gulp air. So the issue might be osmosis if you are certain nitrite and ammonia is not the cause. 



Dr Mike Oxgreen said:


> There also seemed to be a migration of snails heading up the glass towards the surface, within half an hour of the water change.



They do that for various reasons and especially when the water conditions are not right, e.g low nitrite/ammonia lingering. Do you have algae issues? Diatoms?


Dr Mike Oxgreen said:


> I boil a litre or so of the rainwater to bring the new water up to temperature.



When you boil the water, you kill the hardness in it. It's a small tank so a little bit may go a long way.
When I've used MgSO4 it swings my TDS pretty heavily.


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## Dr Mike Oxgreen (16 Apr 2016)

There's no measurable hardness in the rainwater - which is why I boil some of that rather than the tap water. As you say, boiling the tap water would destroy some of the hardness that I want. Any hardness in the rainwater is completely negligible compared to that in my Woking water.

I normally only test after the water change, otherwise it would get expensive. But next time I'll test before and after.


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## sciencefiction (16 Apr 2016)

You don't need to test before and after each time, just for now as means to figure out what's happening. If you haven't tested your tank water recently then chances are it's very different to the water you are adding.  It may not be but I'd go the extra mile and investigate if they were my fish and make sure I am not shocking the fish each time.


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## dw1305 (16 Apr 2016)

Hi all,





sciencefiction said:


> I wouldn't think the rainwater's oxygen content is the problem because in order for it to cause stress it means the remaining 50% of water in your tank is severely low on oxygen and it's easily tipped by the new water. An airstone or heavy surface agitation should fix that within 30min or so if that's the case.


Because the water from the butt is cold, it should hold more oxygen, but if it was de-oxygenated it would form a layer at the bottom of the tank. I use rain-water, but I draw it off the night before I use it. You can't test for dissolved oxygen (with-out a seriously expensive DO meter), but you can test the conductivity with a TDS meter, it should be below 100 microS. 





sciencefiction said:


> there's something "fishy" in the rain water.


Distinct possibility at this time of year because farmers are spraying Wheat etc with insecticides.

Can you add some _Daphnia_ to the water butt? I work on a simple rule,  *if the water has swimming Daphnia it is OK to use*. They use _Daphnia_ a lot for <"water bioassays">, because they are sensitive to a whole range of biological pollutants. <"Evaluation of _Daphnia magna_ as an indicator of Toxicity and Treatment efficacy.......">.

cheers Darrel


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## GHNelson (16 Apr 2016)

Hi
Prime could be the culprit!
hoggie


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## Dr Mike Oxgreen (17 Apr 2016)

Adding some daphnia to the water butt is a good idea, might do that.

From what I've read, Prime only causes oxygen depletion when grossly overdosed. I'm adding 0.5ml to a 20 litre tank. Don't think that's going to be causing any problems.

I have ordered an oxygen test kit which should arrive tomorrow so hopefully I'll be able to confirm or eliminate that possibility soon.

I personally think it's unlikely that I'm shocking the tank with wildly differing water parameters. I do a 50% change with the same 'recipe' of water every week, which means that the parameters of the tank water are strongly influenced by the parameters of the weekly water change. Any alteration of the tank parameters in the meantime would have to be rather rapid in order to take the tank water significantly away from the parameters of the water change. There's probably a small downward drift in KH and GH (plants use the calcium and magnesium, and I believe nitrifying bacteria use carbonates), and a small upward drift in TDS due to accumulation of excess plant nutrients (although offset by the reduction in hardness) - and the pH of the tank water will be slightly lower than the new water due to CO₂ etc.

If I were to match my water change parameters precisely to the water in the tank each time, that would allow the tank water to continue its downward KH/GH drift, resulting in dangerously low buffering capacity. I think it's important that the new water continually 'resets' the tank water and pulls it back to desirable parameters, and provided the difference isn't too great that shouldn't be causing shock - especially since I'm not keeping hyper-sensitive species. I have kept freshwater tropicals for many years in the past, and have never before worried about precise matching of water change parameters - the only thing I'm doing differently this time is using rainwater from a butt.

My next water change will be Friday, give or take a day. I will do before and after water tests on the tank, including TDS measurements. My prediction is that there won't be a big enough difference to account for any fish stress.


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## PARAGUAY (17 Apr 2016)

Quite a lot of fish breeders use rainwater to create conditions for the fishes Neon Tetras as a example you could just be unlucky were your location is as been mentioned by Darrel


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## Dr Mike Oxgreen (17 Apr 2016)

Well, my oxygen test kit arrived today, which is extraordinary since I only ordered it yesterday afternoon!

I have tested both the tank water and the rainwater from the butt, and I do think oxygenation could be a problem.

The tank water measured somewhere between 5 to 8 mg/l, which according to the leaflet is okay but not particularly high for water at 25°C. The lights have been on for only an hour, so the plants haven't had much chance to re-oxygenate the water yet. The HC and Glossostigma are not yet pearling. I will re-test later this evening when the lights have been on for longer.

The rainwater from the butt measured only 2 mg/l, which is the lowest level that the kit can indicate. For water at outside temperature (probably about 10°C), that is very low. Given that this is the lowest level the kit can indicate, it's possible that the rainwater is even lower in oxygen than this.

So, I think that a 50% water change using water that consists of 75% of the rainwater that is very low on oxygen, when the tank's water is "okay but not high" means that there might well be an oxygen problem.

Next water change, I will definitely prepare the water the day before, and aerate it overnight - then I'll measure the O₂ content.


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## Tim Harrison (17 Apr 2016)

I know it seems obvious now but back in the day I seem to remember the so called experts recommending aerating the water butt constantly to stop the water stagnating...maybe there was something in it.


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## Dr Mike Oxgreen (17 Apr 2016)

I can well imagine that it was standard practice back in the seventies to keep an air stone inserted in one's butt to maintain aeration.


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## Tim Harrison (17 Apr 2016)

Absolutely...give it a go I'm sure it'll work well for you...


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## Nelson (17 Apr 2016)




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## Dr Mike Oxgreen (20 Apr 2016)

I forgot to answer sciencefiction's query about algae...

At the moment I have fairly low algae. I have a few small tufts of what looks like black brush algae (BBA), but it sometimes develops the 'antlers' characteristic of staghorn so I'm not exactly sure which type it is. Does staghorn algae have a juvenile form that looks a bit like BBA? Or is it even possible that there's some kind of symbiosis going on between those two types of algae? Anyway, this is a very minor problem; it is not spreading or growing at all rapidly.

Until a couple of weeks ago I had an outbreak of long green threads, and also much shorter velvety green algae in patches on the wood and Anubias leaves, plus a few green spots on the front glass. At that time I had a two hour period of light in the morning at 25% brightness - the purpose being to wake the fish so that I can feed them each morning. I decided that this might be the cause of my green algae issues so I reduced the brightness right down to 5%, which is still enough to wake the fish. Since then, the green threads and spots have vanished and the green velvet is slowly declining.

So as it stands now, I have only a few small tufts of BBA or staghorn and small, dwindling patches of green velvet that's starting to look a bit threadbare where the shrimps have nibbled it. The algae seems to be struggling to cling onto its existence, which is good!

I definitely don't have any diatoms - I did have brown filamentous diatom while the tank was maturing, but that suddenly packed its bags - possibly coincident with my starting to dose the TNC Complete at 2-3 times the regular dose.


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## dw1305 (20 Apr 2016)

Hi all,





Dr Mike Oxgreen said:


> The rainwater from the butt measured only 2 mg/l, which is the lowest level that the kit can indicate. For water at outside temperature (probably about 10°C), that is very low. Given that this is the lowest level the kit can indicate, it's possible that the rainwater is even lower in oxygen than this.


Does the butt have a sealed top? The water in the butt should remain oxygenated, if there is access to atmospheric gases, assuming that there isn't a lot of organic matter in the bottom of the butt (which would decompose).

Even though I have diverters, or a strainer, on the down-pipes, I still tend to get bit in the water butts (mainly moss and lichen from the roof) and I give them a clean out every 18 months or so.

cheers Darrel


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## Dr Mike Oxgreen (20 Apr 2016)

Hi Darrel - yes, the butt does have a lid. Perhaps I'll try leaving it off and see if that makes a difference.


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## dw1305 (20 Apr 2016)

Hi all, 





Dr Mike Oxgreen said:


> the butt does have a lid


A lid shouldn't matter, unless it is very tight fitting? I always have nightmares about our cat and/or birds etc drowning themselves in the water butt, so I check the lids are on most days.

cheers Darrel


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## Dr Mike Oxgreen (20 Apr 2016)

Yes, it's pretty tight fitting - difficult to pull off, in fact!


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## alto (20 Apr 2016)

sciencefiction said:


> Ottos can breathe from the surface and if oxygen is the issue, they'll be the least stressed ones in the tank, plus they'll shoot to the surface to gulp air.


I'm confused on this ... it's my understanding that oto's gasp surface air to fill "sacs" that are then used to control "flotation" (I'm saying this all rather badly) but they are unable to actually utilize that stored air for oxygen.

Aplogies* Dr Mike Oxgreen*  for the hijack 
- rather more on topic, do you add the water with splashing? also filter surface movement?


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## Dr Mike Oxgreen (20 Apr 2016)

I think some fish can gulp air into their digestive tract and the blood vessels can take some oxygen from that air; I don't know if loricariids such as Otos can do this.

When adding water back during a water change I tend to pour the water over my hand to minimise disturbance to the tank. My filter return is via a spray bar mounted low down, pointing upwards up the rear glass. This gives very gentle flow and agitation, which I think is in keeping with the chili rasboras that I'm keeping. Provided I keep my stem plant (Pogostemon erectus) pinched back so that it doesn't block the water surface, I tend to get enough forward flow across the surface to transport CO₂ to the front and somewhat downward to my carpet plants.


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## sciencefiction (20 Apr 2016)

alto said:


> I'm confused on this ... it's my understanding that oto's gasp surface air to fill "sacs" that are then used to control "flotation" (I'm saying this all rather badly) but they are unable to actually utilize that stored air for oxygen.
> 
> Aplogies* Dr Mike Oxgreen*  for the hijack
> - rather more on topic, do you add the water with splashing? also filter surface movement?



My apologies for your confusion.
I am not entirely sure of the biological mechanism but they can utilise aerial oxygen.  In nature they are found in rather stagnant conditions as well. Here is a random scientific paper about it:

"_Loricariid catfishes have evolved several modifications of the digestive tract that


appear to fWIction as accessory respiratory organs or hydrostatic organs. Adaptations


include an enlarged stomach in Pterygoplichthys, Liposan:us, Glyptoperichthys,_

_Hemiancistrus annectens, Hemiancistrus maracaiboensis, HyposWmus panamensis, and_

_Lithoxus; a U-shaped diverticulum in Rhinelepis, Pseudorinelepis, Pogonopoma, and Pogonopomoides;_

_and a ringlike diverticulum in Otocinclus. Scoloplacids, closely related

to loricariids, have enlarged, clear, air-filled stomachs similar to that of Lithoxus. *The*_

_*ability to breathe air in Otocinclus was confirmed*; the ability of Lithoxus and Scoloplax_

_to breathe air is inferred from morphology. The diverticula of Pogonopomoides and_

_Pogonopoma are similar to swim bladders and may be used as hydrostatic organs."_

source: http://www.auburn.edu/~armbrjw/Air.pdf


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## Tim Harrison (20 Apr 2016)

Just put an air-stone in the butt for now, at least then you can rule it out, and take it from there...falsifying hypothesis!


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## alto (21 Apr 2016)

Thanks for the link ... still don't see how they actually proved anything though  - reasoned supposition based upon morphology isn't quite the same

Some of my scepticism is watching my own oto's -  after they rise & gulp air, then return to lower in the tank, I still observe expected gill movement so I'd want more evidence than the author's contention that he did not observe gill movement in his own oto's after surface gulping 
- note that I seldom observe the gulping behaviour.

I did recently observe a severely distressed oto at the surface on it's back gulping air, then rolling, returning to inverted position, more gulping ... all the while also pumping gills - this poor fellow arrived in a recent shipment that did not go well (bags fouled etc though shipping had proceeding according to schedule) He was DOA an hour or so later.
Very few of the otos in the shipment engaged in the surface behaviour - those that did were among the most stressed (& mostly dead )





> Because of the different shapes of the diverticula
> 
> 
> and the notion that _Otocinclus _and the
> ...


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## dw1305 (21 Apr 2016)

Hi all,


sciencefiction said:


> The ability to breathe air in_ Otocinclus _was confirmed





alto said:


> Thanks for the link ... still don't see how they actually proved anything though


I've got the reference from the Armbruster paper somewhere, it is from an un-published Ph. D thesis.

Jay Nelson at Towson has done some work on <"quantifying air breathing in Loricariids">, but I don't know if he has worked with _Otocinclus_ (and I don't have access to the paper). 

The ability to extract oxygen from atmospheric air is thought to be derived from the common ancestor of the Loricariidae and Callichthyidae (they are both families in the superfamily Loricarioidea), but it has been lost in rheophilic species (_Hypancistrus_ spp. etc). They still gulp air in times of oxygen stress, but they can't extract any oxygen from it. 





alto said:


> - note that I seldom observe the gulping behaviour.


I haven't either, but I know from threads, on PlanetCatfish etc., that people who keep _Otocinclus _in less well oxygenated tanks assume that it is standard behaviour. 

cheers Darrel


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## alto (21 Apr 2016)

Thanks for chipping in Darrel 

 (hmmm not sure I said that right  - contributing, I mean)


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## Tim Harrison (21 Apr 2016)

I reckon it could well depend on the species...mine have always darted up to the surface to gulp air even in my low-energy tanks which have always been very well oxygenated.
Like SF has said apparently the digestive tract adaptations that allow them to "air breath" is a diagnostic trait of the genus. 
Loricariids are mostly facultative air breathers but I've heard/read somewhere that may not be true of all oto species...in that some maybe obligate air breathers


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## sciencefiction (21 Apr 2016)

_Otocinclus_ spp.  A duct forms at the junction between the esophagus and the stomach and expands into an enlarged, ring-like diverticulum, diagnostic of this genus, which allows air-breathing.

Personally, during the winter I  may not see otocinclus gulping air at all. In the summer when my tank's temps go up to 28-29 they start doing it and it is then I start worrying because it's a sure sign of low oxygen. As Troi says they are probably facultative breathers. They do survive in stagnant waters in dry seasons alongside corydoras species so they must have a mechanism to extract oxygen.

Here in this video Ivan Mikolji mentions otocinclus and corydoras in relation to their very high tolerance of low oxygen conditions. (at around 11:20)  He's filming pools of water created by the preceding rain season which eventually get cut out from the main river. He says that normally the only species that remain are those tolerating these very low oxygen water pools, mentioning the air gulping behaviour of corydoras and otocinclus.




And here is another one of locals catching otocinclus in those same stagnant pools before they dry out completely. Look at the amount of otos in one catch...!


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## MickeM (22 Apr 2016)

Dr Mike Oxgreen said:


> When doing my 50% water change, I use 9 litres of rainwater from my water butt, mixed with 3 litres of unsoftened tap water. This gives me roughly the 3° KH and 6° GH that I'm after, and I can tweak the GH up a bit by adding MgSO₄ solution if necessary. I use Seachem Prime as my dechlorinator, and use a full-tank dose (only 0.5ml for my ~20 litre tank, so it would be impossible to measure any less). I boil a litre or so of the rainwater to bring the new water up to temperature.
> 
> I often notice that the gill rate of my Otocinclus has risen dramatically after a water change, and this seemed particularly bad yesterday. They were also very restless, and the chili rasboras were nervous as well - schooling very tightly and patrolling the tank rapidly. Most of the blue cherry shrimps seemed fine, but I did see one swimming very erratically and seeming to have difficulty staying upright. There also seemed to be a migration of snails heading up the glass towards the surface, within half an hour of the water change.
> 
> ...



Hi Dr. + all ..

I`m new to this forum but not new to keeping tanks..
I`ve kept tanks for more than 30 years..

Have you checked the NH4+(ammonium), NH3 (ammonia) and pH in the tank + the butt..?
When changing that large amount of water at once.. the pH in the added water+tank water plays a significant role if the "resting"/existing amounts of NH4+ is high i your tank.. (A lot of "restproducts" in the tank-system so to speak..)

When/If pH raises to over 7 in your tank, the NH4+ may almost immediately turn into even worse poisonus and aggressive NH3..
..which may then destroy the gills on fishes (shrimps??) very fast, and as I`ve understood it..it is almost irreversible, .. and therefore making it impossible for most fishes to absorb oxygene from the water..
This may explain the sudden "panic" behaviours from your fishes + shrimps!!??

This same situation may happen if you get some newly purchased fishes in a very "contaminated" transportation-fish/plastic-bag..
..and are adding water with a high pH in it... acute suffication may occur !!!

This may also explain why all the _Otocinclus_ in the film never gets bad.. even if the pool/pond is heavily contaminated(from what it looks..) ..the pH is probably lower than 7...!!!??

I don`t know if this is accurate for what happened to your tank, but it may be worth thinking of..??

/Micke


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## Dr Mike Oxgreen (22 Apr 2016)

MickeM said:


> Have you checked the NH4+(ammonium), NH3 (ammonia) and pH in the tank + the butt..?


NH₃/NH₄⁺ in the butt measures zero. The tank also always measures zero. I haven't measured the butt pH.



MickeM said:


> When/If pH raises to over 7 in your tank, the NH4+ may almost immediately turn into even worse poisonus and aggressive NH3..


That shouldn't be happening because I'm using Prime as my water conditioner, and dosing a full-tank dose with each water change (largely because it's impossible to measure a smaller quantity). Prime converts ammonia, nitrite and nitrate to much less harmful forms.

I never see any positive ammonia reading, either in the tank water or the new water. I rather doubt that there's enough NH₃/NH₄⁺ around to cause damage, regardless of the pH.


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## Dr Mike Oxgreen (22 Apr 2016)

Right, I have done the water change.

I prepared the new water yesterday afternoon, using 8 litres of rainwater, 3 litres of unsoftened tap water, and 10ml of the MgSO₄ solution that I mentioned earlier (which is enough to raise the whole tank's GH by about 0.5°). I aerated with an air stone, which has been running for about 18 hours. Before adding this water to the tank, I boiled another litre of rainwater and mixed it in to bring the temperature up.

I measured the O₂ levels of the tank (before the change) and the new water. The tank, which has been in darkness overnight, measured only 2mg/l, whereas the new water measured about 5mg/l. I'm not sure I believe the absolute values, because surely at that level the fish in the tank would be showing signs of distress, but they were all behaving quite normally and the Otos' gill rate was slow (1 or 2 per second). However, I'm quite willing to believe the _*relative*_ readings, namely that the new water was better oxygenated than the tank, having been aggressively aerated for a long period. I suspect this kit under-reads.

The parameters of the tank water *before* the change were: Temp 25.0°C, TDS 139, pH 6.5, NO₂⁻ 0, NO₃⁻ 40, KH 3°, GH 5°, O₂ 2mg/l

The parameters of the tank water *after* the change were: Temp 24.7°C, TDS 121, pH 7.0, NO₂⁻ 0, NO₃⁻ ~30, KH 3°, GH 6°

So, there is a modest reduction in TDS, accounted for largely by the reduction in nitrate (and probably other excess nutrients as well). This is, after all, the whole point of changing water - a moderate reduction in TDS seems inevitable when doing a water change.

The pH change is inevitable, since I'm adding CO₂ depleted water (the drop checker always goes a bit bluer after a change). Probably the removal of organic wastes would also contribute to this - which is, again, the whole point of changing water. I don't see that there's much that can be done about that.

I didn't bother re-measuring the oxygen content because I know that it would have gone up, although only slightly and I don't think the test kit would be able to indicate the change.

It's too early to assess the behaviour of the chilies, because the lights are still off - but within minutes of refilling the tank, the Otos' gill rate had risen sharply, although perhaps not as dramatically as last week and they're not behaving unsettled.

I'm beginning to think that this is just a slight 'panic' reaction in the Otos. It's certainly true that they do sometimes panic and swim about wildly when I'm pruning plants etc. Last week it may have been worse because I did the water change with the lights on.


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## dw1305 (22 Apr 2016)

Hi all,





Dr Mike Oxgreen said:


> I measured the O₂ levels of the tank (before the change) and the new water. The tank, which has been in darkness overnight, measured only 2mg/l, whereas the new water measured about 5mg/l. I'm not sure I believe the absolute values, because surely at that level the fish in the tank would be showing signs of distress, but they were all behaving quite normally and the Otos' gill rate was slow (1 or 2 per second). However, I'm quite willing to believe the _*relative*_ readings, namely that the new water was better oxygenated than the tank, having been aggressively aerated for a long period. I suspect this kit under-reads.


They won't be accurate values, measuring most dissolved gases is pretty difficult. You really need a DO meter. 

I would assume that your aerated butt water was pretty fully saturated with oxygen, I would be a little bit worried that the level for the tank at night was 1/2 that level. Levels in mg l-1 (ppm) dissolved oxygen can be converted to percentages if you know the water temperature, atmospheric pressure and conductivity of the water, although in fresh water you can ignore conductivity, and to a large extent, atmospheric pressure. Chart below.




 

We use these at the moment <"Hach HQ40d portable..">, with <IntelliCAL™ LDO101 Rugged probes>, these are the best DO meters we've had, but it is quite an expensive option. You still need to calibrate the meter in water vapour saturated air before use, but it doesn't constantly need re-calibration.

cheers Darrel


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## ian_m (22 Apr 2016)

Actually, remembering back to the late 80's when my friend had marine fish and using rain water was all the rage, many people had issues with rain water killing fish. This was traced to leaching preservative from roofing felt/underlay, fitted under tiles in modern houses. Normally this felt/underlay never comes into contact with water, but at the lower ends of the roof, it often dips into the gutter and it was here it was leaching into the rain water. The collected water was fine for plant watering but fatal to fish.


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## Dr Mike Oxgreen (22 Apr 2016)

dw1305 said:


> I would assume that your aerated butt water was pretty fully saturated with oxygen, I would be a little bit worried that the level for the tank at night was 1/2 that level.


On the basis that the fish were behaving normally, and the Otos' gill rate was nice and slow, I don't think there was an oxygenation problem in the tank before the water change.

Also, on the basis that the new water almost certainly _increased_ the oxygenation of the tank water, yet the Otos' gill rate immediately increased markedly, I think we can rule out oxygen as being the cause.

I'm fairly convinced that the results from the kit are highly dubious!

Maybe next time I'll go and buy some RO water and use that instead of rain water, and see if there's any difference. Perhaps as Ian says there's something in the rainwater that I can't detect, and that has a temporary effect - the Otos' gill rate has now slowed down to normal, so whatever the problem was was temporary.

I must confess I've been squinting at that chart and I can't figure out how to use it! I'm probably being dense.


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## Dr Mike Oxgreen (22 Apr 2016)

I've found the explanation of how to use the chart:  you draw a straight line between the temperature on the top scale and the oxygen concentration on the bottom scale, and where it intersects the sloping line gives the percentage saturation.

What I can't find anywhere is a rough value for oxygen concentration and/or saturation below which fish will start exhibiting increased gill rate. I guess it varies from species to species, but ball-park figure?


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## sciencefiction (22 Apr 2016)

Dr Mike Oxgreen said:


> The parameters of the tank water *before* the change were: Temp 25.0°C, TDS 139, pH 6.5, NO₂⁻ 0, NO₃⁻ 40, KH 3°, GH 5°, O₂ 2mg/l
> 
> The parameters of the tank water *after* the change were: Temp 24.7°C, TDS 121, pH 7.0, NO₂⁻ 0, NO₃⁻ ~30, KH 3°, GH 6°



What is the Kh of straight tap water? In order to get a KH 3° in mixed rain/tap water in proportion 9:3, , your tap water must have a Kh 12°, That's nearly double the Kh of my hard tap water here and it looks unlikely to me your tap water has that high of a KH. MgS04 doesn't alter the KH.  Unless there's something in the rain water that adds to the KH... which is again unlikely if its pure rain water.

Something doesn't look right to me in those tests and final results.  I'd switch the CO2 off for a day next time to get a non-co2 PH of the tank water. Also, you may not be really matching the conductivity/TDS of the new water to the tank water because you are adding MgS04 to the mixture. I know you said it only raises the Gh by 0.5° but I'd be curious to know by how much it raises the TDS of the new water mixture? What's the TDS before and after you add the 10ml MgS04 to that12 litres of mixed water?

Have you tried just ignoring any KH, GH measures, forget about the MgSO4 to match Gh, etc......Don't use any tests bar the TDS meter and  mix tap and rain water to get your desired TDS, e.g. 120ppm if that's what you want to be the target long term TDS. This may take a different proportion of tap/rain water, depending on your tap water. For example, my tap water has a TDS of around 250ppm straight out of the tap. To get a TDS of 120ppm I'd need a mixture of 50:50 tap/rain water or just slightly lower on the tap part.


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## Dr Mike Oxgreen (22 Apr 2016)

sciencefiction said:


> What is the Kh of straight tap water? In order to get a KH 3° in mixed rain/tap water in proportion 9:3, , your tap water must have a Kh 12°


It's been a while since I checked the tapwater GH/KH, because the water is so hard that a test uses up vast quantities of the titration solution. But yes, my tapwater is around 12° KH. If your water measures 6° KH, then that's not what I call hard - I've lived in and around the Thames valley all my life so I'm used to very hard water, with chalk from the Chilterns.



sciencefiction said:


> MgS04 doesn't alter the KH.


Erm... I know. I add it purely to increase the GH slightly, for the health of my shrimps.



sciencefiction said:


> Also, you may not be really matching the conductivity/TDS of the new water to the tank water because you are adding MgS04 to the mixture. I know you said it only raises the Gh by 0.5° but I'd be curious to know by how much it raises the TDS of the new water mixture?


It doesn't matter in the slightest what effect it has on the new water; the only thing that matters is what effect it has on the whole tank when it's added and mixed with the existing water. Clearly my 'recipe' doesn't cause an increase in TDS to the tank.



sciencefiction said:


> Have you tried just ignoring any KH, GH measures


No, I'm not going to ignore GH and KH. KH is important for pH buffering, and GH is important for the formation of my shrimps' exoskeletons. I think you're too obsessed with TDS to the exclusion of anything else.

And if I _don't_ add the MgSO₄ then the resulting TDS will be even lower. So what do you suggest I add in order to prevent that swing?


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## sciencefiction (22 Apr 2016)

Dr Mike Oxgreen said:


> It doesn't matter in the slightest what effect it has on the new water; the only thing that matters is what effect it has on the whole tank when it's added and mixed with the existing water. Clearly my 'recipe' doesn't cause an increase in TDS to the tank.



Of course it does. Your water recipe is as close to your tank water as mushroom soup is to carrot soup. They are both soup but are entirely different.



Dr Mike Oxgreen said:


> No, I'm not going to ignore GH and KH. KH is important for pH buffering, and GH is important for the formation of my shrimps' exoskeletons. I think you're too obsessed with TDS to the exclusion of anything else.



I am not obsessed with anything at all. The MgS04 won't help the shrimp. They need calcium. What I am trying to explain to you is that you can't match the stats properly using the liquid test kits. As a result you are swinging the stats without realising it because you trust those test. I won't insist anymore. It's your tank.

As for my tap water...it is hard. I get calcium deposits on the glass.....  You don't necessarily need to have a high Kh when the Gh is high.  My Gh is around 13-14.

Perhaps if you give the full stats of your tap water, the exact Ph of your tank water without being affected by injected CO2, and the TDS of the rain water, it may be easier for others to help.


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## Dr Mike Oxgreen (22 Apr 2016)

You're telling me I'm trusting tests too much, yet you're demanding that I test my water more.

Sorry, but you're talking absolute rubbish. I'm close to clicking the 'ignore' link.


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## Dr Mike Oxgreen (22 Apr 2016)

Oh, and "my GH is around 13-14"

Hahahahahahahaha!!

That's not hard water! You have no clue what it means to live in a truly hard water area!


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## sciencefiction (22 Apr 2016)

Dr Mike Oxgreen said:


> You're telling me I'm trusting tests too much, yet you're demanding that I test my water more.
> 
> Sorry, but you're talking absolute rubbish. I'm close to clicking the 'ignore' link.



I asked that you test your water in order to see if what you are adding together makes up what you want to achieve.  It doesn't look likely to me. The tests can be used as guidance but that's about it. For some reason when using a GH and Kh test as a guidance when mixing water, one doesn't achieve a consistent result from mixture to mixture.


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## MickeM (22 Apr 2016)

Dr Mike Oxgreen said:


> NH₃/NH₄⁺ in the butt measures zero. The tank also always measures zero. I haven't measured the butt pH.
> 
> 
> That shouldn't be happening because I'm using Prime as my water conditioner, and dosing a full-tank dose with each water change (largely because it's impossible to measure a smaller quantity). Prime converts ammonia, nitrite and nitrate to much less harmful forms.
> ...





dw1305 said:


> Hi all,They won't be accurate values, measuring most dissolved gases is pretty difficult. You really need a DO meter.
> 
> I would assume that your aerated butt water was pretty fully saturated with oxygen, I would be a little bit worried that the level for the tank at night was 1/2 that level. Levels in mg l-1 (ppm) dissolved oxygen can be converted to percentages if you know the water temperature, atmospheric pressure and conductivity of the water, although in fresh water you can ignore conductivity, and to a large extent, atmospheric pressure. Chart below.
> 
> ...




OK..
One thing which then comes to my mind..

In case of any modern kind of soil (with nutrients "loaded" inside) is used in the tank.. are not the nutrients then actually just waiting to be chemically "set free"..??

and..if a soil contain high values of "reactively prepared ammonium"(in some/any form?) ..will then not some of this "soil-amount" *+ *the normal "tank-amount" from restproducts be released in form of ammonia at once when adding all this new water??
*If  *this is the case..then I also guess the reaction would be more harmful to the fishes/shrimps at a waterchange of 50% than for example 20-30%..??

And..since ammonia also is a gas right..and it might not be able to detect very easily..?? (as Darrel says )

So *maybe*..?? ....
When adding 50% new water (to the tank-water with pH 6,5)  -  pH+ammonia might be raised..  and then suddenly dropped again...  as a following effect by an active CO2-system..?? (without being detected.. due to the time-factor..fast raise+fast drop!!?? )
If so... An interesting info would be to know how long time passed from the moment you/the Dr. added the new water.. to the moment when measuring the NH4+/NH3 and pH??

and also...
How fast can a CO2 system drop the pH back to below 7 in this situation??? (Ofcourse it is depending on tank-volume, what CO2-system used, the amount of changed water+ all the chemical water parameters...)

This could/would then still explain the panic behaviours of the fishes+ shrimps I guess???

.. and ofcourse.. if any substance/liquid lowering the pH used in the added water..
these effects on the fishes+shrimps will/may hopefully never occur.!!??


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## sciencefiction (22 Apr 2016)

Dr Mike Oxgreen said:


> Oh, and "my GH is around 13-14"
> 
> Hahahahahahahaha!!
> 
> That's not hard water! You have no clue what it means to live in a truly hard water area!



I have a "clue". I don't find any of this funny.  I think you are upset over my comments. My apologies.


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## BigTom (22 Apr 2016)

Can we keep it civil please chaps  

Lots of good discussion in this thread, let's keep it constructive! 

Sent from my HUAWEI GRA-L09 using Tapatalk


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## dw1305 (24 Apr 2016)

Hi all,





Dr Mike Oxgreen said:


> What I can't find anywhere is a rough value for oxygen concentration and/or saturation below which fish will start exhibiting increased gill rate. I guess it varies from species to species, but ball-park figure?


Depends on the species of fish but prolonged periods of anything below 2ppm DO is usually regarded as fatal for most fishes, and even short incidents below 5 ppm would impact on salmonids, or really rheophilic Loricariids.

There are some UK figures here <"Environmental Quality Standards for Dissolved Oxygen">.

cheers Darrel


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## dw1305 (24 Apr 2016)

Hi all,





Dr Mike Oxgreen said:


> That's not hard water!


 I think the thing is that once you get past a certain threshold point, for both plants and animals, it doesn't really matter what the exact figures are.

I think for Red Cherry Shrimp the lower threshold is somewhere just below 4dKH/dGH. I've bracketed them together, because most of the hardness in UK tap water is from CaCO3. I have no idea what the upper threshold is, but my suspicion is that it is going to be above the upper limits of any of the tap-water available in the UK.

Threshold values are going to differ from species to species,Crystal Red Shrimp need softer water etc.

I don't know what the exact figure is for the lower threshold for Red Cherry Shrimp is, because I didn't measure the dGH/dKH, but when I found that I didn't have any shrimps left the conductivity had slipped below 60 microS.

cheers Darrel


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## Dr Mike Oxgreen (26 Apr 2016)

dw1305 said:


> Hi all,Depends on the species of fish but prolonged periods of anything below 2ppm DO is usually regarded as fatal for most fishes, and even short incidents below 5 ppm would impact on salmonids, or really rheophilic Loricariids.
> 
> There are some UK figures here <"Environmental Quality Standards for Dissolved Oxygen">.
> 
> cheers Darrel


Thanks Darrel.

I've just tested the tank water's O₂ level using the kit. The lights have been on for at least four hours, and both the HC and Glossostigma are pearling and oxygen bubbles are continually rising from them. I assume this means the water is pretty much saturated, which at 25°C should mean in the region of 8.5mg/l. Yet the kit only registers 5mg/l. So there's little doubt it under-reads.


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