I went to a friends house for lunch today and noticed they had gotten a fish tank. Its about 2-3 gallons and its one of the "cutesy" kits you can get from a fish store. She has a dwarf puffer in the tank and has had it in there by itself for about 2 months. When looking at it I noticed it seems almost skinny and has a sort of shrunken in back half of the main body. What do think is causing this? She said she feeds it flake food and that it eats it. Is it because they need other foods such as snails or brine shrimp? She doesn't have a test kit so I couldn't look at the parimeters but she says she does about 30-40% water changes every week. What do you guys think? I told her I would look into it for her.