Hello all, I've had my betta since it was a baby in a 10 gallon filtered heated lightly planted tank feeding him a variety of food and he has been very healthy and happy until the last Monday. The fish is now on the bottom of the tank not moving much, has a slightly swollen pale belly and seems to be "heavy" when swimming. He goes to the surface every now and then and then it sinks again to the bottom. I managed to get him to eat some pea yesterday but nothing ever since. I don't want to lose this guy. Water parameters are fine. On sunday I did the partial water change as usual and ever since he is going downhill. I did a 50% water change yesterday too. I used some Sera Baktopur (it is a acriflavin/methylene blue med - to help him breathe, I've read that methylene blue binds oxygen or sth).