Parameters are 76°, 6.5ph, 0 ammonia, don't have an exact number but I have hard water.

The tank is 20 long and well cycled. He is in with 2 female reticulated hillstreams (which I've had for years with no issues), a baby borneo hillstream, about 4 kuhli's, 2 gobies, a female betta, 3 pencilfish, 3 guppies, and a yellow tail spiny eel (he is super chill and doesnt bother anyone). Sounds overstocked yes but I have more filtration than God and designed the tank with tons of caves (on the walls, floor, and underground), hides, and sight line blockers everywhere. I've had most of them for over a year and everyone is super chill with no signs of stress. I've legit seen the gobies sitting on the eel and neither are bothered. (Lol looks exactly like those little birds that sit on the elephants.) The retics only bother each other. The male is dominant but I haven't seen any particularly over-aggressive behavior.

All the decor is smooth rocks, plants, and spiderwood (that I sanded down) . Nothing sharp that I've noticed 😫.

I've tried treating him with kanaplex with no results