Literally overnight my betta's caudal fin is half gone. Attached is a picture from yesterday (4/16) and today (4/17).
Here are the changes,.. fully cycled tank for the past 2 months, BUT I did an 80% water change to add a new substrate. The tank still has old filters, plants and decor. One detail is that the old water was dark (which I didn't like) from Almond Leaves. Temp is 78.
Only tank mate is a nice little Rabbit Snail.
Let me know what you think? API Water parameters are pH-6.6 AMM-0 NO2-0 NO3-0
Also, I think I may have hard water..which could be a reason his pectoral fins are crinckled.
ANyways. If you can, I would love your thoughts.