Too much co2

[mooregary24]

Hi
I am using pressurised co2 which i am monitoring with a drop checker. It stays pretty stable but i notice some of my fish gasping and their giles moving quite alot. Does anyone use spray bars or air stone whilst using co2 or does that not work? When i turn my c02 down my drop checker turns nearer to blue,so it is working ok.

Regards Gary

 

[nry]

Air stone will drive off the CO2 so not good due to the increased surface agitation. Some use one at night when the CO2 is usually off.

 

[wearsbunnyslippers]

water has an amazing carrying capacity for dissolved gases. you use an airstone or spraybar to drive off co2 and increase oxygen in the water. fish gills work by diffusion, so if the co2 concentration reaches a certain level, the co2 stops moving out of the gills and into the water, the fish will then start to suffocate. this is regardless of how much oxygen is in the water.

drop checkers arent the best way of monitoring co2, they are really just an indicator. monitoring your fish, or a ph controller is the best way of controlling co2. if your fish are gasping, turn it down a tad, wait a few hours, then check again, and adjust down further if necessary. using an airstone or spraybar will just server the same effect as turning down your co2.

i have noticed that changes i make on my regulator are not noticed immediately, unless i really crank it up or down, slight quarter turns or less, need a few minutes to register while the pressure equalizes. so never make changes especially increases and then leave your tank for long periods.

 

[dw1305]

Hi all,

but i notice some of my fish gasping and their giles moving quite alot

Fish will be stressed by the CO2 level before they show any physical signs, so you definitely need to turn the CO2 down. Sub-lethal stress will eventually kill your fish. "Wearsbunnyslippers" is correct, the reason the fish are having trouble breathing is that the concentration of CO2 in the blood, in their gills, is not much higher than the level of CO2 in the water and diffusion rates along this gradient are fairly small. The other problem is that the haemoglobin binds with both CO2 and oxygen (O2), if the CO2 is not diffusing out into the water that haemoglobin is not available to bind with the O2 and the blood leaving the gills (and returning to the body) is then not fully oxygenated.

Again as the other posters have said the problem with more surface agitation is that CO2 is more soluble in water than O2, so the loss of CO2 will occur more quickly than any gain in O2 (but diffusion rates will depend upon both the concentration gradient across the water air boundary, as well as the gas solubility). The problem here is that the atmospheric level of CO2 is about 0.03%, so the 20ppm CO2 is about x40 the atmospheric level, leading to a very steep concentration gradient for CO2.

After you have turned the CO2 down, it might be worth thinking about whether you have enough biological filtration capacity, the reason for this is that both the "ordinary" microbial breakdown of organic matter, and the bacterial conversion of ammonia to nitrate are oxygen intensive processes.

Could you run an air pump at night? once the CO2 is turned off?

cheers Darrel

 

[ghostsword]

I would like to add that while your fish may become used to the high concentration of CO2, the issue becomes more apparent when adding new fish, so keep that in mind when you buy new stock.

It has happened to me that I purchased three SAE's, during aclimatation lost one while in the bag, the other two went belly up but managed to recover them. They are fine now, but CO2 is a silent killer, and it strikes hard.

Most people are using CO2 and using the fish to monitor the levels, stopping only when the fish are gasping at the top, but sometimes that is too late already, one change in the tank and very quickly you can end up with a high mortality rate in the space of an hour or so.

CO2 is a major killer and that must not be underestimated.

 

[mooregary24]

Thanks for your replies

Recently i have lost several new stock but my long term fish are fine. I watch for my tiger barbs as they seem to be a good indicator of the co2 level. I have been using my drop checker for quite a while now and it was pretty accurate at a lime green colour. After turniing my c02 down now it is a deeper green and the fish seem happier. Do most of you monitor your c02 levels via ph (ie. API test kit) ?

 

[Burnleygaz]

Are you using 4DKH water in the drop checker or tank water?

 

[mooregary24]

Are you using 4DKH water in the drop checker or tank water?

Hi I am using 4dkh water in my drop checker.


Just to give you all an update on my last posts, I had done a water change on Sunday and i filled the level up higher than i normally would thus decreasing the surface ripple. So i have now re-adjusted my level and my fish are alot happier so maybe i can increase the c02 back to where it was. Always something simple sorts it out. I could'nt understand it as i never really have to alter my c02 and it stays a nice lime green on my DC. Hopefully i can get back to watching tv now rather than sitting in front of my tank. I am considering running an air stone at night but i think i have enough timers in my cainet.

Thanks everyone for sharing your experience with me.
Until my next problem , cheers Gary