Migrated him to a 5g tank about a month ago, with some hiding places, a filter, a heater, and a nice fake plant. He was fine until a few days ago when his tail started looking very ragged. I did a 20% water change and tested after I noticed the tail. I think the tank is cycled since the test was 0 ammonia / 0 nitrite / ~5ppm nitrate. The temperature goes between 78-80F. Since then, his tears seem worse and part of his top fin is almost completely ripped off. He is swimming around pretty agitated. The only other thing I notice that could be causing tears is the protective sponge cylinder on his filter. I just took that out tonight after I noticed his fin. You can sort of see it in this clip along with the tatters in his back fin. ( sorry the light isn't great.) IMG_20170712_202345 by fogfish posted Jul 12, 2017 at 11:05 PM What should I do? More frequent water changes? Put him temporarily in a 1 gallon tank with pure salt & water changes? Thanks in advance for your help.