Fishes CO2 poisoning

[Allan Asis]

Ok for 2 months i've been using a DIY CO2 solution (yeast/sugar) to fertilize my planted tank with CO2. There was only a single incident of CO2 poisoning on fishes since and it was my fault for doing a water change and DIY CO2 solution replacement at night and immediately turning light off after (yes that was a boneheaded move I know!).

Last week I finally move on to the next level and installed a more stable and reliable solenoid regulated CO2 tank (2 liters). However, everytime I turn it on, the fishes start gasping for air and staying on top of the tank until I turn off the CO2. I already reduced the CO2 bubble rate to like half a bubble per second.

My tank size is 66 liters (2 feet) and although I'm guilty of having too many fish in the tank (more than 30 tetras... and a few of otocinclus), I feel that even if I remove most of them and leave just 10 fish, those left in the tank will still suffer CO2 poisoning. Although I failed to do this experiment today because I broke my second tank (which I bought as pre-owned today) while I was cleaning it . However, I will try this and probably just use a big tub. I have a second canister filter that I have been cycling for a long time in a tub.

So has any of you experienced CO2 poisoning on your fish before? I'm a bit puzzled by this because the bubble rate is already the same as when I was using DIY setup before? Can it be that DIY CO2's output is not pure CO2 thus the concentration is much lower than the one in the CO2 tank?

[bennyc]

Hi Allan,

You might wish to get a CO2 checker to estimate the CO2 level. Slighty better than guess works. (it is a form of poisoning, one equipment leading to another)

i did experience over doing Co2 before, major causalities. to achieve the best level, start from a low level and slowly increase to the optimum level, by guess work or by Co2 checker.

Just guessing here, i think the difference between diy and canister Co2 is Canister CO2 is pressurized. So more CO2 per cubic metre.

My view is having many fishes in a planted tank is ok. Most choose not to, because they prefer the planted part to be the focus. i do believe having more fishes is more difficult to balance but playing around to find the right balance is also what makes it challenging/fun of this hobby. when you achieved that it does gives a sense of satisfaction.

[Shadow]

Half a bubble per second is very low for 2ft tank because I'm injecting 3bps using inline diffuser. I have ~30 ember tetra, ~10 sundadanio and countless cherry shrimps, no problem. Do you use reactor or diffuser although I do not thing much of the different? what is your pH reading before and after CO2 injection? What king of soil/substrate do you use? some soil like ADA have pH buffering.

[Allan Asis]

Hi bennyc,
That's the terrible experience I am dealing with now, fishes are dying. Even after the incident, the survivors somehow developed complications likely due to stress from the poisoning and a fish die in like every 6 hours.
This experience is makes me think of giving up as it's very hard to watch these fishes suffer. But I really love this hobby so I have to soldier on.
Your idea of difference between canister CO2 and DIY makes a lot of sense!

As for the fauna, I'm desperately trying to bring up the second thank so I can move the remaining fishes there. It was supposed to be ready yesterday but a freak accident (as mentioned in my other post) caused me to break the tank
Anyways, I figure out that the tank can be fixed as the crack is small and not really a straight line crack that might get bigger in time. So this morning I bought a aqua-silicon sealant and in the process of sealing the cracks. Hopefully by tonight It will be dry enough to test out with water. The filter (canister type) for this tank is already cycled for more at least 6 weeks so it's ready to go. If everything goes smoothly, I should be able to move the fishes in this tank tomorrow

Once that is done I can focus on the plants in the main tank as they are dealing with problems of their own as well. Over the last couple of weeks plants started to wilt and just 2 days ago the new leaves are smaller and curled. Monte carlo and pearlweeds' new leaves look burnt so it seems that they are suffering from nutrient deficiency. I've been dosing seach flourish, iron, potassium, nitrogen, and excel to feed them for about a week now but the inconsistency in CO2 supply (due to poisoning) may be causing them to not absorb these fertilizers efficiently.

It's a learning process and hopefully this experience makes me more seasoned with this hobby in future.


Hi Shadow,
That's the ideal situation that I want to be in, but perhaps I was a bit too aggressive and immediately put in a lot of fish before allowing plants and water parameters to stabilize? I don't have problem with ammonia/nitrite/nitrate as they are consistently 0.0 ppm except for last night when ammonia jumped to 0.25ppm possibly due to the dead fish but I took them out already. This morning ammonia level has settled back to 0 ppm again.
My issue now is pH. Here are the parameters that I consistently get since I started setting this tank up:

pH: 6 (but this is the low limit of API test kit so the real value can be much lower)
KH: 17.9 ppm (1)
GH: 107.4 ppm (6)

As you can see, my carbonate hardness is super low which from my understanding can cause a huge swing on water pH level when supplied with CO2. Even though I was aware of this in the beginning I did not bother to mess with it as from what i've read I might do more harm than good if I am not sure what i'm doing. Also when I was using DIY CO2 I didn't really have issue with poisoning.
The soil I am using is GEX aqua soil (light green packet for plants) but I topped it off with a black quartz. I believe the aqua soil will lower the pH but the quartz is inert, correct me if i'm wrong on that one.

My issue now is that I have no way of knowing the PH swing when CO2 is on, as even when there's no CO2, my pH level is at the low limit of API test kit already.

Another thing to note is the filter media. I dymax volcanic media (branded lava rock lol!) and ANS sintered glass noodle type media. From their labels they are not supposed to alter pH level but i'm not really sure since I never tested it.
The Eheim substrat pro (ball like porous material) brought pH down to 7.0 in my experiment which matches its specs saying "pH neutral".
Seachem matrix confirmed to be inert as well as it did not change water pH in my experiment.
The water I used in the experiment is from tap and measured at 7.6pH (could be more as this is already max limit for API test kit.

[Urban Aquaria]

You'll definitely need a Co2 drop checker to monitor the Co2 levels in your tank... without it you'll be guessing alot more and have to rely on the fishes themselves to check Co2, hence casualties will tend occur.

Co2 from pressurized tanks is definitely more "pure" than that from DIY systems, hence the Co2 concentration is much higher per bubble injected.

30 tetras and a few otos is still a relatively okay bio-load for a 2ft tank, i guess most likely its the sudden changes in Co2 concentration while you are still adjusting the system which affected the weaker fishes.

Usually when changing Co2 systems, like bennyc mentioned, its best to start low first and then adjust the Co2 injection very slowly in small stages, so that the fishes can gradually adapt to it over the period of a few days.

The ideal BPS injection rate is very subjective and will differ from tank to tank (even those of the same volume), it depends alot on the efficiency of the diffuser system, the types and density of the plants, circulation, light intensity/duration, nutrients, livestock bio-load etc. You'll have to tweak it over time to find the best combination.

Just an example, i currently also run just 0.5-1 BPS in my 2ft planted tanks and the drop checker is a constant light green during lights on with plants pearling, but that's in part because i'm using inline reactors which achieve near 100% Co2 dissolve rate. Previously when i used in-tank diffusers and inline diffusers, i was injecting up to 2-3 BPS in order to achieve equivalent Co2 levels in the same tanks.

[Goalkeeper]

I had a bad experience with this before when I forgot to turn off the CO2. I had a timer but I accidentally switched off the timer which essentially on the co2 the entire night till next day when I reached home. All fishes grasping for air and Yamato shrimps half dead. I change the water immediately and blast the water with oxygen using the air pump. Luckily all survived but some Yamato are slightly curled up....am guessing from the side effects of the excess co2. Good lesson learnt.

[Allan Asis]

You'll definitely need a Co2 drop checker to monitor the Co2 levels in your tank... without it you'll be guessing alot more and have to rely on the fishes themselves to check Co2, hence casualties will tend occur.

Co2 from pressurized tanks is definitely more "pure" than that from DIY systems, hence the Co2 concentration is much higher per bubble injected.

30 tetras and a few otos is still a relatively okay bio-load for a 2ft tank, i guess most likely its the sudden changes in Co2 concentration while you are still adjusting the system which affected the weaker fishes.

Usually when changing Co2 systems, like bennyc mentioned, its best to start low first and then adjust the Co2 injection very slowly in small stages, so that the fishes can gradually adapt to it over the period of a few days.

The ideal BPS injection rate is very subjective and will differ from tank to tank (even those of the same volume), it depends alot on the efficiency of the diffuser system, the types and density of the plants, circulation, light intensity/duration, nutrients, livestock bio-load etc. You'll have to tweak it over time to find the best combination.

Just an example, i currently also run just 0.5-1 BPS in my 2ft planted tanks and the drop checker is a constant light green during lights on with plants pearling, but that's in part because i'm using inline reactors which achieve near 100% Co2 dissolve rate. Previously when i used in-tank diffusers and inline diffusers, i was injecting up to 2-3 BPS in order to achieve equivalent Co2 levels in the same tanks.

I actually have a CO2 drop checker in the tank, but for the life of me they have always been "yellow". I followed the instructions saying use the aquarium water to fill it up along with the solution. But from what I read so far in this forum is that it's advisable to prepare a solution from distilled water and baking soda (with sodium bicarbonate) and mix it up until you get a carbonate hardness of 4 dKH. Then use that water to fill the drop checker along with the solution. Am I on the right track for this?
I do have a KH/GH test kit (API) and distilled water and baking soda can be easily sourced out in the grocery store.

As for CO2 reactor, I have my regulator tapped onto a glass diffuser straight up. I really am considering a reactor (those tube you can connect in series with outflow from a canister filter and connect CO2 tube there to diffuse it) as it seems like the best option for long term but this is a second priority at the moment. Once I get this drop checker done and working as intended I'll move onto sourcing out a good equipment for this. Any brand or type you can recommend btw?

By the way the second tank is finally up and running and is leak free now! Some fishes are going to move to that tank tomorrow!

[kurty]

I Just bought of co2 checker over the weekend..
Well, trial and error..

I actually killed a couple of tetra and oto due to overblast of co2..

With the checker, it doesn't help much too..
Color, is neither green, yellow, blue, its like different blend..

Maybe you try the ista brand instead?

[Urban Aquaria]

I actually have a CO2 drop checker in the tank, but for the life of me they have always been "yellow". I followed the instructions saying use the aquarium water to fill it up along with the solution. But from what I read so far in this forum is that it's advisable to prepare a solution from distilled water and baking soda (with sodium bicarbonate) and mix it up until you get a carbonate hardness of 4 dKH. Then use that water to fill the drop checker along with the solution. Am I on the right track for this?
I do have a KH/GH test kit (API) and distilled water and baking soda can be easily sourced out in the grocery store.

Yeah, mixing the Co2 indicator reagent with aquarium water will create incorrect readings in tanks which use active soil substrate... its because the tank water pH and kH is already buffered by the soil so it affects the measurements (Co2 levels are measured by the pH and kH relationship), hence you see it always yellow.

You definitely have to use 4dkH reference water (ie. water with known pH of 7.0 and kH of 4.0) to mix with the indicator reagent, then the color readings will be correct. You have to make sure the solution is mixed properly though, or else the readings will still be inaccurate.

Alternatively you can just buy the pre-mixed Co2 indicator solutions from brands like Ocean Free or ISTA, no need to mix and can use straight away, solve all the possible mixing issues.

[mUAr_cHEe]

Previously when i used in-tank diffusers and inline diffusers, i was injecting up to 2-3 BPS in order to achieve equivalent Co2 levels in the same tanks.

Did you experience micro-bubbles in your tank when you were using the inline diffuser before?

[Urban Aquaria]

Did you experience micro-bubbles in your tank when you were using the inline diffuser before?

Yeah, previously when i was using inline diffusers, the whole tank look very misty, all the suspended micro Co2 bubbles floating around... from a distance it looks like the tank got haze.