Please help... our Betta, Oscar is looking rather bloated and his belly has a whitish colour - he also seems to be off his food. He shares a tank with a snail, no live plants and his water is changed every 2-3 weeks - not a full change only about 25%. There is no filter in the tank and he gets no direct sunlight - he is 18 months old and has always been healthy. We put anti-chloride drops in his water. He is fed on Betta fish food twice a day - he never seems to eat more than he can manage. If food left over we remove it or snail greedily sucks it up. Any help will be appreciated.