I have a male betta that was very healthy, then he started sitting at the bottom, then was floating at the top, stopped eating and whenever he tried to swim to the bottom he just floated back up. I noticed half of his dorsal fin (?) was gone and thought is was possibly fin rot. Since he was having difficulty swimming I moved him to a small tank will a low water level. Since he wasn't eating I ruled out swim bladder, treated him with kanaplex according to the directions. Which was 1x every two days for three treatments. Mr betta got better, so I moved him back to the 3 gallon tank and within 4 days he started getting sick again. I do not want to treat him again until I get some advice.
Before putting Mr Betta back in 3 gallon tank I completely cleaned it, left the gravel out, put 1 sick plant in and changed the small world filter. Yesterday I switched the filters back to the tetra.
3 gallon tank
Filtered - started out using tetra whisper (2 months) and switched to small world (1 month). After a month is when I started having problems. I do have 3 other tanks setup the same way with male bettas and just started noticing problems with fin rot on all three.
Heated to 80
I do a 50% water change every other day.
PH is 7
ammonia levels stay right around 0
I vacuum the tank weekly.
I have well water and the PH level is over 8, so I use 4 gallons softened reverse osmosis water and 1 gallon well water. This gets the ph level down.
I use tetra water conditioner, aquasol (for preventative) and atison's clear almond.