If I remember right, that shark will get too big and agressive for a 29 gallon. I'm not sure if I'm thinking of thr right species, but I think so. You might want to add some cories, or a school of small tetras.
The red tail shark won't necessarily get too big, they can just be a bit aggresive and boisterous for some fish species.
A group of some kind would probably be a good idea.
How long has your tank been set up? This can affect what species would be suitable as some fish need tanks that have been set up longer so are more mature and their water conditions are more stable.