S.O.S.! Over the last week my Neon Tetras have been dying off steadily and I can't figure out why. I started with a nice school of about 25 and now I'm down to the last three or four. They're in a 90 gallon planted tank with all community fish, mostly tetras, livebearers, corys, etc. My water parameters have been pretty steady at:
PH = 7.9 (I know this is a bit high as they like more acidic water, but see the kicker below)
Nitrates = between ~5 ppm
Nitrite = 0
Ammonia = 0
Hardness = 140-160 (Moderate Hardness)
KH/Buffer = 55-70 (on the low side, but I don't have big swings in PH)
Water Temperature 77-78F
Here's the kicker! I have a 45 gallon, planted, community tank with pretty much the same water parameters and my Neons are thriving in there.
I just can't figure it out. They look healthy, too. No visible signs of disease or fungus or parasites. So frustrating. Any help is appreciated. Oh, and yes, I do regular water changes and use Prime to dechlorinate.