I give 4 pellets a day. 2 in the morning and 2 in the evening. I soak flakes in water and also cut them before feeding. It is because I do not want any food at the bottom. I give them pieces of pellets. and they catch from my finger.
I heard that flakes are not the best food. Though myself I feed flakes too(Betta Min). I do not know what kind f flakes you have. But I give more than 4 a day.
After he recovers try not to starve him.
I think he will be better if he still can eat pea. Maybe because of cold water and not best diet heis immune system failed and he got ill.
Before you set up and sycled big tank I woul recommend the way I keep my boys now.
I would recommemd to get at least 2,5 G glass tank (13-15$ in Petco). On my photo. I devided it.
Small heater. I have Marina heater. Bought at Pestsmart for about 10-12$.
The top you can make from any plastic box (just to cut out the plasctic).
Vacume for gravel (or just tube).
When I change water every day (50%) I vacume the bare bottom with tube (I do not have gravel).
You could change water every next day. As Nicci Lu
said the temperature must match.
They seem ok with such rutine and do bubble nests every day.
I do not recommend plant in not sycled tank as you will get nitrites. I already took off most of them and left only one branch of plant.