Hi there!

How about making it into an aqua-terraria and putting some Fire Bellies in there? They are very funny frogs to watch and are quite active.
Avoid mixing species. I know it can be tempting but it can never be a good thing for the animals. There's just so many things that can go wrong.

In such a huge viv I'm sure you can add fish. You need to do frequent water changes tho to prevent the toxins from the frogs to hurt the fish. A large tank as this could house alot of frogs too but remember that alot of frogs = alot of food that you need to have availible.