Ok, I know these types of questions have been asked a bunch of times but I think my tank is a little unique cause of how tall it is. The vivarium measures 20x18x30" (LWH). I'm going to have about 4" of water in the bottom and the rest will be planted including a lot of woodwork and cocobedding covering the back wall.

How many darts do you think I could keep? Right now I'm thinking leucomelas or tinctorius. Everything I've read says that 5 should be ok in a tank like this. Also, I know that mixing is a no-no but is it a big no-no if the mixing is between frogs like leucs and frogs from the vent. family? I really like some of those guys even though they are so tiny.

Thanks!