# 1 Year On and Many Fish Deaths



## Creature Seeker (1 Apr 2020)

I've now been running CO2 for a little over a year and recently took the decision to turn it off. Having kept fish for many years with no problems, over the last 9 months I've had no end of fish deaths spread out over that period. A had three different shoals of 5-10 large African tetras, and I am now down to my very last tetra. I find they usually develop wounds to their sides and around their mouth, which isn't helped my medication, and die after a week or so after the symptoms first develop. It's also been very isolated to just tetras. I have perches, flying foxes and knife fish who have all been fine.

I've always been fairly modest with my CO2 injection, with the drop checker always a good colour green, and never yellow. 

Has anyone else had trouble keeping fish with CO2 injection? I've read a lot of mixed views searching through Google so wanted to ask the experts.  Other changes I've made to the tank in conjunction with the CO2, was a lighting upgrade and dosing once a week with tropica Premium Nutrition, but thought the CO2 was more than likely the culprit.

Any helps greatly appreciated.

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## Dr Mike Oxgreen (1 Apr 2020)

How often do you do water changes?

Fish health problems are so often caused by poor water hygiene or raised levels of pollutants.

It sounds like you’re doing nothing wrong with CO₂.


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## Creature Seeker (1 Apr 2020)

About 35% every 2 weeks, cleaning filters every other water change. 

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## jaypeecee (1 Apr 2020)

Hi @Creature Seeker 

Have you measured any water parameters over the last few months? The following parameters may give us a clue:

KH, GH, pH, Ammonia, Nitrite, Nitrate

I assume you are using tap water. If so, which tap water conditioner do you use?

Do your fish ever gasp for air at the water surface?

Which fish medication(s) have you been using?

That'll do for now.

JPC


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## PARAGUAY (2 Apr 2020)

I have never had fish trouble with CO2 except the odd "keep your eye on things" while setting it because things can quickly go wrong . Move the drop checker around or have 2 to give a better indicator. How  are you cleaning your filter ? Sounds like a water quality problem
.


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## Simon Cole (2 Apr 2020)

You probably need to check for granulomatous inflammation. Carbon dioxide poisoning typically has different symptoms and is less group specific.


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## Dr Mike Oxgreen (2 Apr 2020)

Dr Mike Oxgreen said:


> How often do you do water changes?





Creature Seeker said:


> About 35% every 2 weeks, cleaning filters every other water change.


I would try doing 50% every week. Since you’re running a “high tech” tank, your plants will be producing a lot more organic waste, which is why you need to do larger and more frequent water changes. In fact you would probably benefit from doing 50% changes twice a week for a couple of weeks, then go down to 50% once a week.

When you clean the filter, are you careful to ensure that you only rinse the media in the old tank water? If you rinse in untreated tapwater the chlorine will kill any helpful bacteria living in the filter. That said, if your tank is heavily planted then it’s your plants that are doing most of the work and your filter is mainly just contributing the circulation of the water.

It would be helpful to check some of your water parameters. It’s very important that your test kit reports absolute zero for ammonia and nitrite. Nitrate is allowed; up to about 50 ppm is reasonable (and most fish can tolerate higher), but lower than this is better for fish health.

However, I suspect we might not see anything untoward in your test results. My bet is that your tank has a high level of “unfriendly” bacteria which are attacking your fish. A regime of frequent water changes is probably the best solution.

I wouldn’t be blaming the CO₂. Carbon dioxide isn’t corrosive and won’t directly cause wounds or infections. The symptoms of CO₂ poisoning are surface gasping and lethargy; if your fish are active and behaving normally then you simply don’t have a problem with CO₂. Personally I would reinstate the CO₂ but if you have decided to switch it off then you will also need to reduce the intensity of your lighting, otherwise you’ll get major algae problems - and you may be able to reduce your nutrients slightly as well.


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## Zeus. (2 Apr 2020)

Dr Mike Oxgreen said:


> I would try doing 50% every week. Since you’re running a “high tech” tank, your plants will be producing a lot more organic waste, which is why you need to do larger and more frequent water changes. In fact you would probably benefit from doing 50% changes twice a week for a couple of weeks, then go down to 50% once a week.
> 
> When you clean the filter, are you careful to ensure that you only rinse the media in the old tank water? If you rinse in untreated tapwater the chlorine will kill any helpful bacteria living in the filter. That said, if your tank is heavily planted then it’s your plants that are doing most of the work and your filter is mainly just contributing the circulation of the water.
> 
> ...



I would skip the testing, frequent 50%+ WC short term the 50% weekly, remove the waste and reset tank weekly


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## lazybones51 (2 Apr 2020)

Like others have said, since adding CO2 I haven't seen an increase in fish deaths. As long as you take the time to dial it in properly, you shouldn't end up with gasping or dead fish.


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## dw1305 (2 Apr 2020)

Hi all,
@Creature Seeker I'm not a CO2 user, I never have been and I never will be. My opinion is that it presents an unacceptable, and unnecessary, risk to fish health. As well as the ever present risk of catastrophic fish death there maybe long term sub-lethal effects.

I know other people have successfully kept healthy fish long term with CO2 injection, but I'm not willing to take the risk.

cheers Darrel


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## jaypeecee (2 Apr 2020)

Zeus. said:


> I would skip the testing...



Hi @Zeus. 

May I ask - why do you advise skipping the testing? This can then be followed by water changes. Knowing something about the water chemistry may provide valuable, first-hand data for the OP, @Creature Seeker. If @Creature Seeker doesn't have the required test kits, then fair enough - skip any tests. But I was also interested in knowing if the OP had any test results from the last few months.

JPC


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## Zeus. (2 Apr 2020)

jaypeecee said:


> May I ask - why do you advise skipping the testing?



Sure M8

Little if nothing to be gain.

1. Test kit unreliable and prone to user error and poor interpretation, esp when we not doing them on a regular basis
2. Cost.
3. Will the result change the treatment? subject to point 1. & 2.
4. Do you have the right test kit handy, if not with lockdown it will be a few days
5. When have a basic history and a Biweekly 35% WC in high tech tank is the obvious main culprit ATM (accumulation of salts and toxics etc) 

So IMO Testing is waste of time in this case as it wont change anything esp shot term. Treat the obvious


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## jaypeecee (2 Apr 2020)

Hi @Zeus. 

OK. It's the OP's call. If @Creature Seeker needs any more information, I'm sure that s/he will ask.

JPC


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## Siege (2 Apr 2020)

Hi @Creature Seeker , what size is your tank? Can you list the full spec, 

Have you got a photo of the whole tank?


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## Conort2 (2 Apr 2020)

Hi @Creature Seeker 

what species of tetra are dying specifically? I have heard of Alestopetersius caudalis dying due to this issue. Apparently the fish constantly spar then develop sores which progressively get worse killing the fish. Eventually over time the shoals gradually dissapear. Not sure if they are a black water species which requires a really low ph thus a very low bacterial count to thrive.

cheers

Conor


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## Creature Seeker (2 Apr 2020)

Thank you for all of your useful replies. It definitely appears that I haven't adjusted the frequency of my water changes in line with the the requirements of a High Tech tank. I have a full testing kit so will test everything and post results. I always carefully rinse the filter sponges in existing tank water I've removed during water changes. I use Aquasafe water conditioner. To treat the poorly fish, I originally used Melatix and Pimafix, but have since reverted to King British to see if that helped, but it didn't.

My tank details are below:

Fluval Roma 240
Lighting front - Aquasky LED 30w
Lighting rear - Fluval Plant 3.0 LED 59w

15x Congo Tetra (all died)
6x Long-finned Tetras - Brycinus Longipinnis (all died)
6x Breuseghem's Tetra (1 left - not well)






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## Dr Mike Oxgreen (2 Apr 2020)

It must be heartbreaking to lose all those fish;  I really feel for you.

Your tank looks fantastic - once we work out what factor is causing a problem, it should be straightforward to fix. I think frequent water changes will be a really good start.

Please, don’t put all that lovely plant growth at risk by turning off your CO₂. I’m virtually certain that’s not where the problem lies.

Together we’ll figure this out!


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## jaypeecee (2 Apr 2020)

Dr Mike Oxgreen said:


> Together we’ll figure this out!



Indeed, we will. Firstly, Tetra _Aquasafe_ is a good choice as it deals with chlorine, chloramine and ammonia. Now, your fish. According to the excellent resource, _Seriously Fish_, Brycinus longipinnis (Long-finned Tetra) is very sensitive to water conditions - particularly nitrate level. Coupled with this, Epalzeorhynchos kalopterum (Flying Fox) can be aggressive to other fish. See:

https://www.seriouslyfish.com/species/epalzeorhynchos-kalopterum/

Neither Melafix nor Pimafix are particularly effective. It is best to think of them as preventatives. Which King British product are you using?

JPC


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## jaypeecee (2 Apr 2020)

Creature Seeker said:


> I have a full testing kit so will test everything and post results.



Hi @Creature Seeker 

Excellent! I look forward to seeing your test results. I suspect they could hold some clues as to where your tank problems lie.

JPC


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## Witcher (2 Apr 2020)

Hey @Creature Seeker where do you get your water from? Tap, RO, rain or mix? As a first thing I'd check water reports from your area across approx one year back and see if there are any significant changes in last year or so. Some parameters could change across the year and while within norm and not lethal for humans or larger animals, they may be unbearable by some more fragile fish.


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## PARAGUAY (3 Apr 2020)

Siamese Algae Eaters would be a better choice than Flying Fox which get aggressive and can stress tank mates out Of course when you sort this out


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## sparkyweasel (3 Apr 2020)

Is that a Climbing Perch I can see in the pic? That's another fish that can get aggressive and injure or harrass other fish.


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## Conort2 (3 Apr 2020)

sparkyweasel said:


> Is that a Climbing Perch I can see in the pic? That's another fish that can get aggressive and injure or harrass other fish.


Looks like a leopard ctenopoma which should be fine with fish that size.

I’d recommend upping your water changes to start off. At least 50percent twice a week. It looks to be a water quality issue and the tetras are certainly more sensitive than your over fish which is why only they may have been affected.

cheers

Conor


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## jaypeecee (3 Apr 2020)

Hi @Creature Seeker 

I'm really eager to know the outcome of this one! Any news yet?

JPC


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## Creature Seeker (4 Apr 2020)

Thanks guys. I'll post all the test results later today. 

Apologies, there was an error in my previous post. I have 5 algae eaters, not flying foxes! I always get those two muddled and they look so similar. I've never noticed any fish attacking any others.

I'm also going to clear out some of the plants. The melon sword fires out shoots which then sprout lots of additional plants. I kept them attached and they drift on the surface as I thought it looked pretty (dark clump to the left on previous photo), but they tend to limit circulation and trap plant detritus. Does anyone want and melon swords on here FOC? It would be a shame to throw them away. I haven't posted plants before, but I'm sure I could figure it out but may need shipping covered if it's more than a few quid. You'd obviously have to quarantine the plants given the issues I've been having!

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## jaypeecee (4 Apr 2020)

Hi @Creature Seeker 

Thanks for the update. Sounds like there'll be more to come later today.

JPC


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## Creature Seeker (4 Apr 2020)

Ammonia 0mg/L
Nitrite <0.1mg/L
Nitrate <5mg/L
Phosphate 1mg/L
PH 6.6
GH 100 mg/L
KH 20 mg/L












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## jaypeecee (4 Apr 2020)

Hi @Creature Seeker 

Nice set of test results and the photos are really helpful (and very clear). There is just one parameter that may need attention and that is KH (20mg/l). This approximates to 1dKH. I always ensure that KH never falls below 4dKH. A good range, in my opinion, is 4 - 6dKH. As you're injecting CO2, there is a possibility that there has been what is sometimes known as a 'pH crash'. When this happens, the tank water pH can temporarily drop to very low levels. So, although your measurement clearly shows a pH of 6.6, it could have dropped to a much lower figure whilst CO2 was being injected. How this may have affected your specific fish I don't know but it is possibly worthy of further investigation.

In order to increase KH should you decide to do so, I have used sodium bicarbonate or potassium bicarbonate for this purpose. Please take a look at:

http://theaquariumwiki.com/wiki/KH

JPC


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## Creature Seeker (5 Apr 2020)

Thanks @jaypeecee .

This morning I've tested both my tap water and my tank following 50% water change (and CO2 off overnight).

Tap water:
PH 8
GH 140 mg/L
KH 80 mg/L

Tank following 50% W/C
PH 7
GH 100 mg/L
KH 40 mg/L


Looks as though the water change is helping the KH. Will do another midweek w/c and test again.

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## jaypeecee (5 Apr 2020)

Hi @Creature Seeker

OK, things are moving in the right direction but it's going to take a few water changes before the tank water KH reaches a figure that I would consider a safe value. In order to reduce the likelihood of a pH crash, your best bet may be to keep CO2 off for a while or reduce injection rate. Dimming your tank lighting should help as it will reduce the rate of CO2 usage by your plants.

Please be aware that a pH crash can kill off the beneficial bacteria in your filter. Nitrifying bacteria reproduction reduces at around pH 6 and they die if the pH gets as low as 5.5. But, this may not be a problem for you as your tank is obviously planted. Consequently, your plants will consume the ammonia excreted by your fish.

Please keep us updated.

JPC


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## dw1305 (5 Apr 2020)

Hi all, 





jaypeecee said:


> Please be aware that a pH crash can kill off the beneficial bacteria in your filter. Nitrifying bacteria reproduction reduces at around pH 6 and they die if the pH gets as low as 5.5.


I think microbial nitrification will be reduced at lower pH, but it definitely won't stop. 

In terms of what we know about nitrification the past is <"definitely a different country">. There are a <"much larger range of organisms"> involved in nitrification than was initially thought and <"many of them are Archaea">, which aren't restricted to <"alkaline, carbonate rich, habitats">. 

cheers Darrel


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## aquascape1987 (7 Apr 2020)

Zeus. said:


> I would skip the testing, frequent 50%+ WC short term the 50% weekly, remove the waste and reset tank weekly





Zeus. said:


> Sure M8
> 
> Little if nothing to be gain.
> 
> ...



I’m sorry Zeus but I too, don’t agree with this at all. I don’t think being dismissive of the potential value of the information a water test may yield is helpful here. I also feel that just resolving the issue with water changes, without  even bothering to try and identify what the cause of the issue is, guarantees no long term experience value for the OP either. After all our past experience is what improves our future knowledge, and benefits us greatly because we learn from our mistakes. But only if we correctly identify what the mistake was.I have read a lot of your posts, and have found them to be very useful, knowledgeable and informative. I have a lot of respect for you, but I don’t  believe that there is nothing at all to be gained by testing...

People always say that liquid test kits are unreliable and not useful yada yada yada,and are prone to user error. My thoughts and experience on this are:

1) They may be unreliable when it comes to trying to match up the colour and determine PPM ,but  in reality, determining the PPM accurately of ammonia or nitrite in a year old and cycled tank is irrelevant, as any detectable level, positively indicates a problem.The test has therefore done its job and has been useful.The tester can then investigate further in the direction of ‘what could be causing this ammonia and nitrite in my already cycled tank?’ , leading to a higher probability of solving the problem. The OP doesn’t know what’s causing the problem, and has more than likely drawn an erroneous conclusion that it is related to his CO2 input.
2) User error is unlikely if the tester follows the simple step by step instructions on the box, which for most people is not a difficult task. I always repeat the test twice or even three times, to ensure that there is no error.

I too do not test at all really, unless I encounter a problem these days. My tank is long since cycled, and it’s inhabitants survive and thrive in there long term, so I have no need to. I did however find a test VERY useful only last week. Had 4 shrimp die over a 2 day period. I also initially, and erroneously  suspected that my CO2 had caused the deaths, as I had recently increased the injection rate.A day later, I found an ancient tube of those crappy tetra test strips in the bottom of my maintenance box, which had probably been lost in there for years. So  just for the sake of it, I dipped one and it indicated high nitrite and ammonia.I was puzzled, and thought that the test was probably a duff, so I dipped another.. Same result.I then got my liquid tests out, which indicated the same. Very high ammonia and nitrite levels. The colours of the tests were as dark as they possibly could have been, so now I’m really puzzled. After immediately getting out as many of my critters as I could, and putting them into my hospital tank full of fresh water, I sat down and had a think about it for about 10 minutes. I then remembered I had added 8 new snails a week earlier, which were now hidden amongst my scape. I tracked all the snails down and found 5 out of the 8 were dead and rotting. They absolutely stunk  After removing them, and doing 3 x 90 percent water changes on the bounce, the test kits now showed and continue to show zero nitrite and ammonia. So you can see here how the test kits proved useful in correctly identifying a serous water quality issue, and also did so without me needing to discern accurately how many PPM my issue was, as it still pushed me down a train of thought that led me find out rather quickly and resolve exactly was killing my tanks inhabitants.


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## Zeus. (7 Apr 2020)

aquascape1987 said:


> I’m sorry Zeus but I too, don’t agree with this at all. I don’t think being dismissive of the potential value of the information a water test may yield is helpful here



No need to apologise I'm all in favour of peer review 



aquascape1987 said:


> User error is unlikely if the tester follows the simple step by step instructions on the box, which for most people is not a difficult task. I always repeat the test twice or even three times, to ensure that there is no error.



Some times its not user error but a limitation of the test kit itself, as @foxfish puts it in quote below



foxfish said:


> The accuracy of home test kits is a much discussed subject on this forum, not so much of late but certainly two or three years ago, test kits were possibly the most debated theme outside of lighting and C02!
> To be honest I never really absorbed  the scientific reasons given but accepted the facts due to the facts being offered, were backed by very confident and experienced people.
> As I remember it, most hobby kits are capable of measuring within reasonable limits but are often influenced by other chemicals that might be present in a aquarium.
> Or in other words (maybe?) if you had a bucket of pure RO water and added a single element then that element might be detected  quite accurately by the test kit but if you then added several other chemicals then the test results might well be effected and become inaccurate?
> I am really not sure if that is a good analogy, maybe someone with a better grasp can explain it better.



The test kit you used that help you diagnose a very high ammonia level payed off  excellent and it help you find the problem and sort it out *completely* which is a great result OFC.  But the ammonia was very high so it would off been a distinctive result as well

However if you had of just done a 50% WC it would of reduced the ammonia by 50% which would of helped but not solved the issue, but your filters bacteria would of already been responding to the excess ammonia and would of continued to increased the speed of which it could handle the high ammonia till it was resolved and IMO it probably would of handled the extra load and the snails would of rotted away to nothing given time and then the bacteria in your filter would return back to normal levels. You may off lost some more livestock, you also may not off. Your test with the test kit you had handy help diagnose the problem and got you searching for the issue........



aquascape1987 said:


> I also feel that just resolving the issue with water changes, without even bothering to try and identify what the cause of the issue is, guarantees no long term experience value for the OP either.



With all respect we wasn't resolving the issue with WC, we was just stating the SOP 'Standard Operating Procedure' for 'EI' Dosing a high tech tech, dose ferts in excess and 50% water changes and no test kits, the OP was doing 35% biweekly. Plus the OP has said that the WC has potentially fixed a problem which the test kit has spotted, if he had been doing the WC as in the SOP the issue may have never happen ! thats if it the kH causing the problem OFC

I have absolutely no idea what my kH is as my tap water is very hard and I just accept it as it is, esp after seeing what T Barr has produced over the years I just copy his SOP and no test kits  (I do have an API test kit I have play with sometimes )


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## Creature Seeker (11 Apr 2020)

Tank following another 50% W/C
PH 7.6 - 8.0
GH 120 mg/L
KH 50 mg/L

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## jaypeecee (11 Apr 2020)

Hi @Creature Seeker

Now that KH is around the 3dKH mark, this should afford some protection against a pH crash. Following your current regime of water changes, you seem to have got that under control. I did previously suggest the following:


jaypeecee said:


> In order to reduce the likelihood of a pH crash, your best bet may be to keep CO2 off for a while or reduce injection rate. Dimming your tank lighting should help as it will reduce the rate of CO2 usage by your plants.



Did you try either of these? BTW, how far into the period of lights ON (aka photoperiod) did you make your KH and pH measurements? If possible, try to do these measurements at the end of the photoperiod. That way, we should see the minimum pH that your tank is experiencing.


jaypeecee said:


> So, although your measurement clearly shows a pH of 6.6, it could have dropped to a much lower figure whilst CO2 was being injected. How this may have affected your specific fish I don't know but it is possibly worthy of further investigation.



Have you been able to find more information about your specific fish species that would help us solve the problem that you are having?

JPC


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## Creature Seeker (12 Apr 2020)

Thanks for your comments @jaypeecee.

I turned the CO2 back off and dimmed the lights as soon as you'd said, and it's still off at the moment. My lighting fades in from 12-2pm, and fades out from 9-11pm. I took the latest reading around 2pm so I'll take another Round 10pm tonight.

I will look into the needs of the fish that died in more detail. I didn't think Congo's were particularly sensitive, but have since read that they can be.

What KH should I be aiming for in mg/l?

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## jaypeecee (12 Apr 2020)

Creature Seeker said:


> Thanks for your comments @jaypeecee.
> 
> I turned the CO2 back off and dimmed the lights as soon as you'd said, and it's still off at the moment. My lighting fades in from 12-2pm, and fades out from 9-11pm. I took the latest reading around 2pm so I'll take another Round 10pm tonight.
> 
> ...



Hi @Creature Seeker 

Thanks for the feedback.

Are your plants still OK now that CO2 has been temporarily switched off and lighting dimmed?

4dKH = 72 mg/l (give or take a gnat's whisker) and that's what I suggested as a minimum figure.

JPC


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## Creature Seeker (12 Apr 2020)

Plants are okay, but they'd been suffering anyway as I'd turned the CO2 off for a few weeks when I'd had the last straw with fish deaths. Some lily leaves have some algae and some of the spindly plants are a bit black at the bottom.

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## Creature Seeker (13 Apr 2020)

Tested water last night. GH and KH the same. PH around 7.4.

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