Weird bubble on betta's ventral fin and a pic of it I just noticed this weird bubble on my betta's ventral fin. I have no idea what it is and I am worried it's hurting him because it is bending his fin into a weird position. I left the house today at 4 and everything was fine. When I got home four hours later at 8, this bubble thing had suddenly appeared. I got some pretty clear pictures, does anyone know what this is? Here is some background info that might be helpful: Tank - 5 gallons that he has all to himself Heater - set to 78F (sometime the water temp fluctuates between 76F-80F, depending on the room temp) Filter - None, because the filter that came with the tank had a really strong current (and I mean really really really strong) so I ordered him a nice sponge filter online and am awaiting delivery. Since there is no filter I have been changing 20% to 25% of his water every other day. Water Conditions - Treated with Tetra Aquasafe -Ammonia 0.25ppm (although once I tested some dirty tank water, some brand new water from the faucet with Tetra Aquasafe, and some brand new water from the faucet without Tetra Aquasafe and all three of them measured 0.25ppm for ammonia) - Nitrite 0 - Nitrate 0 - PH 7.5 History - When I got him 3 months ago his dorsal fin was pretty rotted, so I kept his water clean and it started to grow back. It got pretty long but then after a month just stopped growing. It stayed the same for like 2 months and then just recently completely fell off even worse than when I got him, and his tail fin has started to shred at the ends. I ordered his filter a few days ago and then went to the store and bought him some tetracycline. The directions said to have aeration, so I went back to the store and bought an air pump and stone and stuff and set it up today. Then I left for 4 hours and came back and the bubble had appeared. I got scared and decided I should give him his first dose of tetracycline right then (and now his water is yellow, but according to the package that's normal I guess). So my two ideas of what this is are either 1. Something to do with the fin rot, or 2. Something to do with the air pump since I just set that up this morning. I know this is sorta long but I just wanted to give all the info I thought might be useful. I also took some pictures and hopefully I can figure out how to get them on here. Any help would be much appreciated!!!