Catfish pellets (not necessarily the most expensive but not aways the least expensive; mixing them is good) plus pieces of fish/whole fish, frozen-thawed. I used to buy 25 lbs of marine fish called spot for $15-$20 from a small local food fish shop. Mix different pellets and different aquatic/sea foods in every now and then.
I catch spot all the time! Just go catch them... i can get about 25 of them good sized in about an hour...
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