Mysterious Deaths - Any Advice?

[locked word]

Hi,

Everything has been stable in my tank for two months. 30 gallon tank - approx 25 fish (all small w/exception of pleco). All of a sudden, the small fish (rummies, endlers, neons) seem to be grouping near the tube that feeds my airstone, and the intake for the filter - the hatchets, penguin, pleco, and cories are still freely moving throughout tank. Yesterday, a penguin's body mysteriously surfaced, and now a neon. Nitrites and Amonia levels testing normal, temp 81, ph a little basic (7.2) - am treating this with sodium biphosphate (normally do an h20 change, but this has been done too recently). Any ideas on what could be causing mystery deaths? No spots - no tears - no fungus appear on any of the fish. No fish are gasping, and rummies noses are bright red (usually a good sign all is well with water).

Any advice appreciated.

Thanks!

 

[black hills tj]

~25 fish in a 30g tank? What are your water params?

 

[locked word]

Too many? We figured we were ok, because the bulk of the fish are small - endlers (guppies), neons, rummies, white clouds, penguins, hatchets. Also, 2 cories and a pleco. We were told when we last went to the pet store that we could add the endlers (last ones added) because they were tiny - but that should be the end of it. I won't add more to replace the lost ones at this point in case this is an overstock issue.

Like I said - amonia and nitrites are testing normal - 0.0 amonia, 0.0 nitrite -- ph a wee bit high at 7.2 , temp 81. We have an air stone running across the back of the tank and good surface agitation.

 

[rich311k]

It may just be one of those things. How often do you change water and how much? Do you know your nitrate readings? I would return the pleco and get a few more cories.

 

[Zagz]

Can you give nitrate reading? Also what is your filtration? When the fish grow to full size you will be overstocked. The pleco alone will out grow that tank.

Your ph is fine, a stable ph is better than trying to adjust for "perfect" ph.

 

[locked word]

Update on the mysterious deaths: FOUR MORE OVERNIGHT! This is an awful epidemic, whatever it is. All of my penguins except one is now gone - the only penguin left is the original agressor.

Three of the four bodies had their stomachs chewed on - do you think this may be the cause of death, or an afterthought/opportunist snack?

Any chance this is neon tetra disease?