I’m pretty new to the game and just joined the forum. I have six Serpae Tetras in a 30 gallon tank. I had to leave the country for 3 weeks and had my wife feed the fish and plants. When I got back I noticed a bubble looking growth on one of my tetras. I tried to look up what it may be but figured someone on here may be able to give me a direct answer. Any help is much appreciated!