Hi vossner,
I just love your fish planters. They are going to be so cool planted.
I agree with Cinta, I would stick with plants that tend to be drought tolerant. I see you are in zone 9, Richmond, TX. That can be some pretty intense sun so you will have to think about what plants can handle full sun in your area. Unless you have a spot with filtered sun/shade?
These two delosperma bloom all summer until killing frost and both will spill over the edge.