i have my fantail in a 5 gal tank temporarily while he recovers from swimbladder issues, and i fasted my golsfish for 2 days, fed 1 pea, fasted another day, and today, im wondering would it be best to feed him another pea or just regular goldfish food?

I usually fast for 3 days, then feed nothing but peas (all he can eat in 2 mins twice a day) for a further 3 days. Make sure that you soak all his goldfish food in a little tank water for a few minutes prior to feeding it after.