I have a 10 gallon tank with 2 small Green Spotted Puffers in it - just got them about a month ago. We recently overcame a horrible case of ich (we lost one GSP) which I treated with RidIch - still treating, about nine days into it (along with Instant Ocean and Melafin)....they seem to have recovered, all ich spots are gone and they seem healthy.
One of my GSP's though, who actually had the worst case of ich, is now VERY thin around the sides (until yesterday he/she had a lot black areas on his belly and around his face, but today those are gone, thankfully) - I'm guessing he/she has internal parasites (My other GSP is still nice and round and healthy looking); they are both eating fine and seem to be active (they used to be REALLY active, but I think they were also adjusting to the tank).
By the way, great site - without you, my little guys might not still be swimming! I am so thankful....I've contemplated going to WalMart to rescue the rest of them as they were labeled as "freshwater"...my husband would kill me because that would mean another big tank, but how can we resist?