If your temps are above 55 but your worried they could still drop your best food to feed would be wheat germ. This will help clean the intesinal tract and get the processes back to work as they should, once temps are holding day and night above 60 then it's time to start mixing wheat germ and a 38%-40% protien based diet, if the temps do drop then drop back on the protein food. Remember feed lightly and only once or twice a day at first and gradually increase with the water temps. Once water temps are holding well in the seventies then 40-42% protein diet should be feed if your wanting good growth for the summer. Water temps here are holding steady at around 70-74 and the fish are eagerly feeding but I'm still only feeding every other day trying to get them moved before I crank them up to full spring feedings.