Is the temperature in his tank low? Sometimes if the temperature is low or if the heater has failed they get cold and their bodies get slowed down. Do you have a thermometer in his tank to check the temperature? He could just still be feeling not well since he had the finrot and all too. So you may have to restart him on some type of med but I need to know more about what he is doing is there some way you could do a vid or pic of what he is up to and post it? Have you tried peas on him?