HELP! Fish Gasping for air

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Prolific Poster
Apr 24, 2005
Well I got my CO2 up to 28ppm yesterday. This morning all the fish and shrimp were gasping for air at the top of tank. I aerated and did 30% water change and all the fish seem fine. I lost one ghost shrimp but my two cherry shrimp have recovered. My pH was at 6.5 with a KH of 54ppm. My lighting is at just under 3w/g.
I also started dosing Seachem Nitrogen and Potassium yesterday. I added 4 ml Nitrogen to 39 gallon tank. My nitrate test kit had read that I had dropped from 5ppm to 0ppm. It is still reading 0 ppm this morning. Potassium was dosed at 5ml per instructions. I have also been dosing Flourish and Flourish Trace starting last week. Tank is heavily planted and the plants have been steadily improving over the last week as I have followed Tom's EI advice.
I have the CO2 disconnected and unhooked one of my bulbs just to calm things down while everything recovers. I'm nervous now about everything but it seems like the problem has to do with the extra CO2 push. Is that right? From what Tom has written it doesn't seem like those levels should be a problem. Should I give the fish some time to recover before I start CO2 again? If so then how much time?
Could it be the Nitrogen or Potassium? Or is there anything else I should be looking at?

Thanks for any help, Bill


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
San Diego, Ca
Re: HELP! Fish Gasping for air

There are a couple things here. First, how accurate are your KH and pH test kits? A little swing in either direction could be disastrous. For example, if your KH is right and your pH is actually 6.4 (A very easy possibility), you're looking at 36ppm instead of 28ppm. Then swing your KH to 71ppm instead of 54ppm and it's a real mess.

Remember, these are very small swings that are well within the probability range of a typical test kit. I'd say let your fish be your guide and cut back 1/3 to 1/2 on the CO2. If they are happy there, bring it back up a little bit. Once they start to get affected again, cut back down just a bit (This is fairly close to what TB has said to do on a number of occasions).

I also wouldn't cut down on your light unless you have completely turned off the CO2. Remember...plants will take the CO2 out of the water if the lights are on ;)

Ian H

Guru Class Expert
Jan 24, 2005
Shipley, West Yorkshire, UK
Re: HELP! Fish Gasping for air

Your problem is lack of oxygen. Make sure you have got some water surface movement, particularily at night. I use a small powerhead and although I inject CO2 24/7 I have no issues with fish gasping. As long as the surface flow is not too vigorous you will not cause any problems with losing CO2.