How long has he been refusing food? IME when a cat slows down feeding and lays low hes just growing and should come back with vigor/appetite. Tempature and season could have a play in the mix also. Not sure what ur weathers like in cali but my specimen will slow down when its cold here in the fall...You cant just feed a cat every day either in my book. If you do, they will eventually shut off for a while on their own as needed to digest and grow. Sporadic feeding is always best IMO, every other day, every day, cple-few days off a week....etc... gotta keep em hungry or there just gonna sit there... Its not good to over pack their bellies all the time either. U can blow an anus out or cause bloat leading to rigimortis lol... My specimen is a big baby. If i annoy him too much with guests, scare/startle him, mess with his space, or dont prepare his fillets properly that day hes known to go sit in the corner and refuse feeding. Ive kept my guy unheated ever since ive had em and his tempature range is 68-76 through the year. average would be 70-72 for the most part. Id stop messing with ur heater, pick where u want it and let it be. changin it around inconstiently could make him shut off feeding also. If your ambient water temp is somewhere between 70-76 id unplugg the heater all together... If hes skinny and ur worried he needs a meal maaybe bump up to 76 and stay there for a while. i dont think ive ever hit 78 degrees. i dont even keep my stingrays that warm consistently.