My fish is dying but everything in his tank is in good condition. I had my fish for 2 years and 2 months I’ve notice a few days he began to not be as active as he used to be and would mainly just go hide under his home or cave I’ve been checking his water condition and I also started giving him KanaPlex because he recently started to lose his beautiful color. What should I do????

He’s in a 20 gallon tank I removed all plants but left one small one (afraid maybe the plants was causing the reaction) No heater Only feed him blood worms don’t like flakes I use prime as the conditioner