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1 Year On and Many Fish Deaths

Joined
5 Aug 2015
Messages
28
Location
Shipston-on-Stour
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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Joined
3 Jan 2016
Messages
383
Location
Woking, UK
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.
 

jaypeecee

Member
Joined
21 Jan 2015
Messages
1,701
Location
Bracknell
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
 

PARAGUAY

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Joined
13 Nov 2013
Messages
1,941
Location
Lancashire
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
.
 

Simon Cole

Member
Joined
25 Dec 2018
Messages
497
Location
Buckingham
You probably need to check for granulomatous inflammation. Carbon dioxide poisoning typically has different symptoms and is less group specific.
 
Joined
3 Jan 2016
Messages
383
Location
Woking, UK
How often do you do water changes?
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.
 
Last edited:

Zeus.

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Joined
1 Oct 2016
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3,635
Location
Yorkshire,UK
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.

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

dw1305

Expert
Staff member
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7 Apr 2008
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11,522
Location
nr Bath
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
 

jaypeecee

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Joined
21 Jan 2015
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1,701
Location
Bracknell
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
 

Zeus.

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1 Oct 2016
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Location
Yorkshire,UK
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
 

Conort2

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Joined
16 Feb 2018
Messages
498
Location
London
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
 

Creature Seeker

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Thread starter
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5 Aug 2015
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Location
Shipston-on-Stour
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)
8cf7d2847ee2ce5bf3f9a5c53da526f8.jpg
095bbec13130dac98a1a915b796128be.jpg


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Joined
3 Jan 2016
Messages
383
Location
Woking, UK
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!
 

jaypeecee

Member
Joined
21 Jan 2015
Messages
1,701
Location
Bracknell
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
 

Witcher

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Joined
15 Jan 2020
Messages
300
Location
London
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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