A few days ago I noticed my betta had developed a huge swelling in his belly. I've had him about a year and its an established tank. He seems fine-swimming and eating normally. Water chemistry is fine with a no ammonia or nitrite. 20 nitrate so I did a partial water change. Have had a bit of a problem with brown algae lately. Could I be feeding him too much? He gets 3 hikari baby pellets daily. Any ideas?