Tank size: 29-gallon
Ammonia - 0
Nitrite - 0
Nitrate - 10-15
GH - 5
Occupants: 2 fancy goldfish: one is about 3" and the other is about 2"
Three live plants
My smaller goldfish has been hovering near the top of the tank, and now he is flat against the substrate. The tank is too warm for goldfish, so I am floating some ice packs to try to bring down the temperature. The goldfish is over a year old and has a deformed mouth, so he's been rather sickly on and off. Both fish were in a 10-gallon tank until three weeks ago when I got the chance to upgrade.
I don't know whether the heat is getting to him (we've no air conditioning and it's nearly 100 outside), if he's constipated, or if something else is ailing him. The transition to the larger tank went smoothly; no ammonia spikes since I put the old filter on the new tank to let the bio-bugs gather on the new filter.
He has no outward signs of illness other than a clamped dorsal fin. No red marks, open sores, bloating, fin rot, etc. The other goldfish is just fine, so I don't think it's a lack of oxygen or poor water conditions, but I could be mistaken.