I see that you have a 55 gallons tank. As usual, I would suggest getting a Striped Raphael catfish. They are the cutest catfish on the market. Striped Raphaels are quick eater, everywhere. Cories are slower than Striped Raphaels. Also, Striped Raphaels will continue searching everywhere for food, until it can not be found. They are good at getting all the food, before the food decompose.
So, from me, Striped Raphael catfish. Now you will get choices from other people on here. From then on, you can decide.
Thunder