Posting your parameters will go a long way in getting help. Also, with the attitude of 'What do I replace it with once it dies', you'll not get very far IMO
I've posted this before, but I have always fed my fish after lights out through a syringe with a piece of air line attached to it. Once they got used to it having food in it, they attack it when it comes in the tank. I feed a variety of frozen foods for 'carnivores', and my cardinal eats them all.
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