pH problem in tank

[Chez_]

Morning everyone. I have been ineffectually faffing around with CO2 in my 400l tank just using a drop checker for the last couple of weeks. I've had one or two deaths and have gone back to basics. CO2 has been off for five days and I did my weekly 50% water change a couple of days ago.

We have done degassed tests (waiting 24hrs) with an NT Labs Narrow test, that read out at 6.8 for both tank water and tap water. I have just tested straight out of the tank and it's 6.2.

I have an FX6 with a spray bar providing quite a bit of surface agitation.

I feed 40ml TNC Complete three times a week and do a 50% water change once a week.

I knew the pH would be low -- our water comes straight off the sandstone and acidic soils of Exmoor -- and I was thinking a .5 drop in the pH would be all I could aim for. However, that will take it below 6 if I am starting at 6.2.

I think that might be bad for the fish? They're a mixture of nano common community fish, tetras, Corey's, bristlenose, Endler's, honey gourami, chain loaches.

Do I need to abandoned the idea of the CO2? Do I need to think about getting the pH up a bit? I chuck cuttlebone in all my tanks.

 

[LMuhlen]

Usually the comparison of the pH drop is made with the degassed sample, so your 0.5 drop would put you at 6.3. A full 1.0 pH drop would put you at 5.8.

Keep in mind that drop tests have a lot of room for inaccuracies.

It seems to me that most fish manage to adapt to CO2 acidity well enough, but it is hard to understand what is a proper adaptation and what is just painful survival. Nevertheless, I'd expect most of your fishes to be OK. Not sure about the endlers.

 

[Bradders]

If you are really worried, you can add some crushed coral to the filter (in a bag) and it should increase (and buffer) the ph. Then, you will feel comfortable that the CO2-induced pH will not be of concern.
I have never done this myself (I live with tap water with a pH of 7.5-8.0) so perhaps some people with experience can chime in.

 

[Andy Pierce]

Have you measured your KH? If that's close to zero there are a lot of gentle ways to increase KH (which also increases pH) to between dKH 2 and 3 or so and then you can inject CO2 as you like.

 

[Chez_]

Thanks everyone for your answers. The KH is 2, using the NT Labs hardness test, which doesn't sound like it's too terrible? I have some crushed coral I could add to the filter if necessary, though.

• Tank size is 400l, but prob 340l filled, I've got lots of wood etc in there. Fluval FX6 with a spray bar that is currently on max, with lots of surface agitation. Two air-stones.
• CO2: 7am - 3pm, one bubble a second ATM. I've got a JBL Spiral 10 diffuser that is in the corner of the tank under the start of the spray bar and near one of the air-stones. Is that the right place for it? My logic is that it's at the beginning of the current, so CO2 bubbles will travel all the way down the tank.
• Lights: 50% 9am-11am - 100% 11am-4pm - 50% 4pm-6pm
• TNC Complete 20ml a day, 200l water change once a week.

I am at home tomorrow and can keep checking on the behaviour of the fish, and then tomorrow night I can test the PH and increase it a bit. Working on the one bubble per second per 80l from George Farmer's book, I should be aiming for four or five. I don't want to do anything quickly though, as I lost a couple of fish whilst faffing around without measuring properly before the holiday.

Any further advice or reassurance would be appreciated. I'm a bit worried it's like a washing machine in there for the fish with the FX6 on max.

 

[hypnogogia]

None of those plants look ‘difficult’ so perhaps you can get away with less than a full 1pH drop - you probably don’t need 30ppm of CO2.

 

[Andy Pierce]

Thanks everyone for your answers. The KH is 2, using the NT Labs hardness test, which doesn't sound like it's too terrible? I have some crushed coral I could add to the filter if necessary, though.

KH of 2 is perfectly fine. You don't need to change anything here.

• Tank size is 400l, but prob 340l filled, I've got lots of wood etc in there. Fluval FX6 with a spray bar that is currently on max, with lots of surface agitation. Two air-stones.
• CO2: 7am - 3pm, one bubble a second ATM. I've got a JBL Spiral 10 diffuser that is in the corner of the tank under the start of the spray bar and near one of the air-stones. Is that the right place for it? My logic is that it's at the beginning of the current, so CO2 bubbles will travel all the way down the tank.

1 bubble per second is wholly inadequate for a 400L tank. If that's a drop checker on the left side of your picture you can see that it is entirely blue indicating that you have added a negligible amount of CO2 under your current conditions. "Bubbles per second" isn't very reliable as a unit of CO2 injection, but I have a tank that is 10x smaller than yours and I inject probably around 3 bubbles per second which gives a not very aggressive CO2 concentration per drop checker... maybe around 10 or 15 ppm.

 

[Chez_]

KH of 2 is perfectly fine. You don't need to change anything here.

1 bubble per second is wholly inadequate for a 400L tank.

Thanks, Andy. I was going to increase daily and keep testing the PH at the end of the day to see where I am at. If I'm aiming for 30 per second-ish then I will turn it up to say, 10 per second as a starting point today and tweak it up during the course of the week.

 

[Connswater]

KH is 2

KH of 4-6 is much easier to manage when injecting CO2. With Hornwort and Vallis - you probably know this, sorry - they are plant species that actually like neutral to hard water and certainly don't need 20-30 ppm of CO2, you could completely rethink your plant choice and exploit your low hardness water and settle for more modest CO2 injection and you could keep a lot of very happy tetras and difficult plants, many of the stem plants love softer water, Rotala Macrandra, Cabomba etc.
Lovely bog wood and sand substrate, and with your soft water, less injected CO2, maybe gentler filtration/surface agitation, a little bit of buffering, lots of soft water plants and soft water fish, and you should see things thrive. Aesthetically I personally don't think your blue background works very well, but more importantly, perhaps, I think a black or brown, or green background settles fish, but that might be an anthropomorphism!
I wish you well, I play with my water hardness but sometimes think I should work with the liquid concrete from the tap - my choices for a hard water would be Vallis, Hornwort and some of the crypts available.

 

[NorthCoast]

KH of 4-6 is much easier to manage when injecting CO2.

In what sense? For using ph/kh table and oh controller?

I’m very new to this but I have been trying my best to understand this as my situation is similar to OP with a smaller tank.

 

[Connswater]

In what sense? For using ph/kh table and oh controller?

I’m very new to this but I have been trying my best to understand this as my situation is similar to OP with a smaller tank.

Good question. And my I don't want to overstate my understanding of science.

My tap water tends to be around 14 KH sometimes higher, never lower. I have to mix it with collected rainwater (which is often in limited supply) to get water <10, it is an effort with evaporation and the natural effect of adding trace elements, to keep the water <10, lower than 6 for me is almost unsustainable.

Karen Randall in Sunken Gardens suggest an optimal alkalinity of KH 3-8. That gives with CO2 injection optimal dissolved levels of CO2 >10 but <30 within the pH range of 6.6 - 7.2. Many find a pH <6.6 problematic with some fish, and plants generally prefer a pH which isn't much above neutral, though there are exceptions. The last think we want is a collapse in pH. Many folks buffer water with a very low KH to prevent a very low pH.

Personally I prefer to err on the side of caution, fish are easily killed.

I aim for a CO2 level in the 10-20 ppm range when the lights are on, and a KH of >6 but <10 that is relatively easily achieved without the threat of poisoning the fish. In fact, in my tanks with timer controlled CO2, levels rise during the initial photo period and level out about 3 hours in, as I don't have CO2 on before the lights come on. I find that this often used strategy can distress fish, O2 levels are at their lowest just before lights on. I get pearling only towards the end of the photo period, I don't aim for the fizzy drinks look. Fierce sustained pearling suggests to me a system operating right on the edge. The latter is fine for plant only tanks and produces very fast plant growth and the plants easily out compete the algae, even though it requires heavy macro nutrient dosing, I don't do the latter, I am a lean dose person. With very low KH things can become intolerably acidic when using injected CO2. I've seen plant damage, melt, with low KH water and CO2 injection, indeed I once saved a plant only tank by stopping CO2 injection and stopping plant melt when the KH was very low.

 

[bazz]

KH of 4-6 is much easier to manage when injecting CO2.

Hi,
I'm afraid I don't quite understand this statement either, any chance of elaborating? I ran my last scape (and also running my current one) at 0.5 dKH without any problems whatsoever, a few on here run their tanks at zero or close to and are some of the best plant growth I've seen.

 

[Connswater]

Hi,
I'm afraid I don't quite understand this statement either, any chance of elaborating? I ran my last scape (and also running my current one) at 0.5 dKH without any problems whatsoever, a few on here run their tanks at zero or close to and are some of the best plant growth I've seen.

I have done my best already, and I haven't tried to think about the effect of Phosphate, that really would be too much for my scientific understanding. I 'cut my teeth' in the hobby with low KH water but in the 1960s and 70s I wasn't injecting CO2.

 

[Connswater]

Hi,
I'm afraid I don't quite understand this statement either, any chance of elaborating? I ran my last scape (and also running my current one) at 0.5 dKH without any problems whatsoever, a few on here run their tanks at zero or close to and are some of the best plant growth I've seen.

I think I know what you are picking up, the amount of CO2 to alter low KH water isn't greater. I perhaps take Randall to literally and that the 1-3 KH range can be fine.

A passage from the Aquarium Science website supports the use of low KH water but > 1 KH.

Many people are under the mistaken impression that a low dKH results in large pH swings when adding CO2, while raising the dKH will result in smaller pH swings. This is not the case for any dKH over 1. The dKH will move the start and end pH values, but the pH swing will be the same for a given level of CO2. You can see this in the charts:

• Example 1: Assume a dKH of 15 degrees and a starting CO2 level of 4.5 ppm, you would have a pH of 8.0. If we then add CO2 to achieve 28 ppm the pH would drop to 7.2, a change of 0.8.
• Example 2: Assume a dKH of 1.5 degrees and a starting CO2 level of 4.5 ppm, you would have a pH of 7.0. If we then add CO2 to 28 ppm your pH would drop to 6.2, a change of 0.8.

This relationship will break down at extremely low dKH levels (below 1 degree), when there isn’t enough carbonate to completely buffer the acids present. In that case, the pH can drop quickly and dramatically. But if the dKH is 1 degree or higher, then the size of the pH swing when injecting CO2 will be determined only by the amount of CO2 dissolved in the water.

 

[dw1305]

Hi all,

I ran my last scape (and also running my current one) at 0.5 dKH without any problems whatsoever, a few on here run their tanks at zero or close to and are some of the best plant growth I've seen.

That one. I always use @Roland's - <"Soft water tank">.

My 70l tank,gh5/6 ,kh1,K15ppm,No3 5/10ppm,po4 0.20ppm

Karen Randall in Sunken Gardens suggest an optimal alkalinity of KH 3-8. That gives with CO2 injection optimal dissolved levels of CO2 >10 but <30 within the pH range of 6.6 - 7.2.

I perhaps take Randall to literally and that the 1-3 KH range can be fine.

It is a shame, she is some-one I have <"a lot of respect for">, but I've read a few of her posts and my opinion is that she doesn't really <"understand buffering">. @Andy Pierce is the person <"you need"> for the chemistry - <"GH,KH, water report and Chatgpt">.

My tap water tends to be around 14 KH sometimes higher, never lower .......That gives with CO2 injection optimal dissolved levels of CO2 >10 but <30 within the pH range of 6.6 - 7.2. Many find a pH <6.6 problematic with some fish, and plants generally prefer a pH which isn't much above neutral, though there are exceptions. The last think we want is a collapse in pH. Many folks buffer water with a very low pH.

I'm not a CO2 user, but my understanding is that you just need a <"drop checker with a narrow range pH indicator (bromothymol blue) and "4dKH" solution">. This means that the carbonate hardness of your tank water isn't really relevant, because only dissolved gases can cross the air-gap into the drop checker and the pH change ("change in the protonation status of the bromothymol blue") is entirely dependent on the amount of dissolved CO2.

It is only the carbonate hardness of the <"4 dKH solution in the drop checker"> that matters. The base in solution (sodium bicarbonate (NaHCO3) etc.) is the <"proton acceptor">.

Because the drop checker has an air gap, the colour change of the bromothymol blue, narrow range, pH indicator is entirely dependent upon CO2 that diffuses across that air gap, and the small proportion of that CO2 that becomes carbonic acid (H2CO3). That is why you have the 2 hour lag period, it gives time for the drop checker to "catch up". I still like the <"bouncy castle analogy">.

The carbonic acid then disassociates (into HCO3- and H+ ions) and it is the "extra" proton (H+) that causes <"the pH indicator to change"> from blue (deprotonated) to yellow (protonated). When you have a mixture of protonated and deprotonated bromothymol blue? It is green, simply because you've mixed together yellow and blue.

If you want a lower CO2 level you can still use a drop checker, but with 2dKH solution.

Personally I prefer to err on the side of caution, fish are easily killed. I aim for a CO2 level in the 10-20 ppm range when the lights are on

That is the primary reason that I don't add CO2 <"CO2 Disaster">. I think that when people get acidosis and fish death they are both <"symptoms of underlying issues">, rather than the former having caused the latter.

cheers Darrel

 

[Connswater]

That one. I always use @Roland's

A very impressive tank. Is it a plant only tank?

Thanks Darrel as always, and I for one, hope I keep a sensibly open mind, and my experiences, though extensive are of course only my experiences.

As you know I do not claim to be a scientist and my tank contains black mollies and tetras, amongst others, so I try, indeed must, practice moderation in all things.

I also try as far as I can to look to natural environments as guidance. Foolishly I wondered, many years ago, how, in a hard tap water area plants grew so well in my ponds, then I measured the hardness, and of course rain water was diluting the hardness. My wildlife pond, much affected by seepage from the soil edges is actually soft, a KH generally <4. Not much higher even when I top up with the hose to compensate for evaporation and transpiration in the summer.

In my tanks I am always trying to find a middle ground to accommodate an eclectic/cosmopolitan variety of fish and plants, like most folks I suppose. Though I do have reservations about trying to combine plants with low and high light requirements, and I don't feel comfortable with high CO2 levels or with the current fashion of running planted tanks cool. Lighting is easier I suppose to vary in a very large tank in which lighting can be more easily adjusted over the tank. And of course barbs and danio species cope well with temperatures in the low 20s.

I think in terms of pH, KH, CO2, macro nutrients and even plant mass, I play safe, I have even witnessed distressed fish before the lights come on if the plant growth is wildly excessive. In terms of filtration, aeration, temperature and lighting, again I tend to play it by 'the book', though which book I suppose.

I'm no youth, and my copy of the Aquarium Atlas which was first published in 1982, author Dr R. Baensch (a Zoologist not a chemist) also states that 'A carbonate hardness between 2 and 8 is recommended', page 33.

There is an interesting table pH modification in relation to CO2 in two water types page 37 Robert Allgayer (a Zoologist) & Teton (I am not aware of his scientific background), The Complete book of Aquarium Plants, pub., 1986. And further, they have a table on characteristics of varieties of water page 13 across a range of environments, only Blackwater is close to zero in Carbonate Hardness, all the rest are 2.5-12.5 except the Rio Candela which is a stonking 40, and CO2 levels range from 0 to a maximum of 18. Nitrates 0-25.

My Dennerle book, again not a recent publication, 1990, suggests 'ideal water values: carbonate hardness 2-4', and a 'pH 6.4-6.9', but does suggest CO2 at 35 which I personally would not want to risk. It also has a table specifically on Carbonate hardness: '1 too low, 2 very good, 4 good, 7 high and 15 too high', yet George Farmer uses very KH hard water with admittedly, a generally easy range of plants and plenty of injected CO2.

The now quite famous Diana Walstad (interestingly a medical biologist by profession) is adamant in her book Ecology of the Planted Aquarium, pub., 1999 that 'if you use CO2 injection. you simply must maintain a certain alkalinity in the water...Your tank should have a carbonate hardness (KH) above 3 or 4', page 93.

Of course these sources may all be wrong, error is often duplicated across a variety of texts. And I, for one, have no graduate or postgraduate scientific training. It will amuse you to know my training was in political science and modern history, though later in life I also acquired graduate theological education. A now 'retired' Anglican priest with a career in political science must not get too sure of himself in matters of science.

 

[dw1305]

Hi all,

Is it a plant only tank?

Possibly it is. This would be a very soft water tank, with fish <"Joe's tank"> and what fish they are.

As you know I do not claim to be a scientist and my tank contains black mollies

Tricky, they really need very hard, alkaline and, ideally, slightly brackish water.

Foolishly I wondered, many years ago, how, in a hard tap water area plants grew so well in my ponds, then I measured the hardness, and of course rain water was diluting the hardness. My wildlife pond, much affected by seepage from the soil edges is actually soft, a KH generally <4. Not much higher even when I top up with the hose to compensate for evaporation and transpiration in the summer.

I have a pond as well, rainwater filled, but full of "Bath stone" (Oolitic limestone) so fully calcium and carbonate saturated - <"Journal - Lockdown wildlife pond">.

I think in terms of pH, KH, CO2, macro nutrients and even plant mass, I play safe, I have even witnessed distressed fish before the lights come on if the plant growth is wildly excessive.

That both "is" and "isn't" caused by the plants as such. <"Plants are net oxygen producers"> and even at night more plants should mean more dissolved oxygen. The "is" bit is because plants are releasing CO2 at night, but it is really a water circulation and gas exchange issue.

Of course these sources may all be wrong, error is often duplicated across a variety of texts.

It isn't exactly that they are wrong, it is just that <"the past is a different country">. Personally I think advising people that to have some dKH isn't a bad idea, I'm guessing that it is only really keepers of blackwater fish and dedicated aquascapers who are going to keep their tanks at very low dKH levels.

cheers Darrel

 

[Connswater]

Hi all, I think JBL's table is interesting I like the distinction made between with and without fish.

 

[Connswater]

slightly brackish wate

That was standard advice when I lived as a kid in Belfast. I suspect, no stronger than that, it was to do with soft water and nitrite. I as you know use softened water but not very soft water and a UV and always have Nitrite at zero (as far I can measure accurately) and a UV system, as far as I am able to tell, my black mollies are healthy, third generation now, but without a UV ever so prone to whitespot. Have a great evening.

 

[Connswater]

Ammonia and Nitrite and low pH water, a useful table from Aquarium Science website, with a low pH you win on Ammonia but lose on Nitrite, expensive processed aquarium soils leach Ammonia for a while after tank set up, good filtration with mature filter media of course should mean no Nitrite: