I’ve had this betta for about a year and two months. I believe she is around 2 years old though. I have her in a five gallon tank with a mix of real and fake plants along with wood for tannins. I was gone for a week for Thanksgiving break and I left her one of those Top Fin dissolving feeder blocks. I’ve used those several times over the past year and had 0 issues with them whatsoever. But this time when I returned I noticed it left some weird grayish residue surrounding it. I used the gravel siphon and removed what was left of it and noticed almost a slight sulfuric smell which was not there before (my tank usually smells kinda like a river). I could tell the smell was coming from the block. She was her normal bluish purple color when I got back and by the time I got back from classes the next day, her fins and the top of her body started turning white. Her behavior is the exact same before, she is energetic, moving with my finger, and gets her food quickly. Can someone please tell me what I can do to fix this or just what is going on in general?
https://i.redd.it/p5mk61nxuo5g1.jpeg
Posted by Merry_berry7785