It's a 6 gallon tank and I change 2 gallons every 2 weeks. Even with
all the plants, with 6 fish my nitrate level does run in the 45-50
range and I've always worried about that, but the fish seem to do
fine. I have not changed or added anything recently so I think I can
rule out a parasite. I looked closely and noticed that one Harlequin
rasbora (over 1 year old) is also looking a little pudgy. Thanks for
the help.