Ed:
Great story. Has to be either catfish or grass carp. Grass carp can get huge, even in small ponds ( I think you call them tanks in TX ).
Grass carp are easy and fun to catch. They have vey small mouths so you have to use vey small hooks, like #10. You can use bread, cookie dough, lettuce, oe even dog food pellets.
Some folks get a kick cathing them with a fly rod.

Have fun. They say they are even vey good to eat.

Mark Jenkins
Memhis, TN