[Spaff]

You don't necessarily need broms for this tank if you're keeping auratus because they do not feed their tads with eggs like pumilio or some of the thumbnail species. These species require broms or film canisters for that reason. The only reason to have broms in an auratus tank would be personal preference. I agree that most will get too tall for this size tank. Maybe look into Cryptanthus sp. These are terrestrial broms that stay farly small in my experience. They also turn a bright pinkish-red in high light.

 

[Spaff]

You can grow them in the substrate as long as it drains well. They will rot if the substrate stays too wet. I've seem them grown mounted in vivs as well. I would cut off the roots it has when you buy it before placing it in the viv. The plant will grow new roots that are adapted to the conditions within the viv reducing the chance of rot.