Sudden Gourami Death Syndrome

[confusion]

Need a little help. I have a 37G cube with 2 angels, 3 dwarf gouramis, 4 swordtails, and 6 ottos. The angels aren't very big yet, btw.

Anyhow, I had a male dwarf - beautiful and full of character. He was great like always, and 10 minutes later, he was dead laying on a plant.

So, I got a new one a few days ago, and I just found the older one dead - he was doing great about 2 hours ago.

Here's my theory. I bought a CO2 system that has an upside down diffuser where it just holds a big bubble of CO2 to be dissolved into the tank. Shortly before each died, I had just replenished the CO2. I have a CO2 meter which shows that the levels are pretty good, low if anything. I'm wondering, though, if the dumb gouramis are taking a gulp of the CO2 and poisoning themselves, dying nearly instantly of suffocation. Seems far fetched, but there aren't any other symptoms.

The tank is cycled - 0 0 and less than 10 (due to plants, I suppose). I change between 30 and 50% of the water each week. I haven't added any medications or the like. The only other thing I've done, though between the two deaths is add a heater.

All of the other occupants are doing well. Any ideas? Is the CO2 poisoning idea far fetched?

 

[WILDER]

Any bubbles beneath the skin on the fish.

 

[confusion]

Nope. No sign of anything wrong physically. His mouth was open like in mid breath

 

[WILDER]

Didn't make a croaking nose when you removed them from the tank.

 

[confusion]

no.

 

[WILDER]

I would just put it down to a bad batch.
How long did you have them.

Don't no anything on C02, I think tolak your man pm him he's nice.

Did a search and found that an overdose of C02 can kill fish.
http/www.thekrib.com/Plants/CO2/

 

[confusion]

the first one that died I had for about 8 months. Awesome fish. he was a regular dwarf. The second one to go I had for about 2 months and he was a sunset (fire) gourami.

I'll shoot tolak a pm. I was thinking that since they do breathe air from time to time that maybe both of them took a gulp of air that they couldn't recover from.

 

[WILDER]

http/www.thekrib.com/Plants/CO2/poison.html

 

[confusion]

So, I hadn't checked my ph in a while, and it seems pretty low - around 6. As I understand it, that's because I have low buffering ability and the addition of the CO2 is likely dropping the ph to levels that the gourami can't handle.

 

[sylvia]

That was just what I was about to say CO2 can dramatically drop pH levels and gouramies are especialy sensitive to such fluctuations. This is almost deffinately what killed the males.

BTW, it's not the low pH per se they can't handle - it's the actual drop (or any change for that matter).

 

[confusion]

I know I'm not the first to deal with this - what is the solution? I think it's to increase the hardness of the water, but how?

 

[WILDER]

http/www.drhelm.com/aquarium/chemistry.html