First of all: LARGE TANK IMMEDIATLY! Don't just contemplate it either, those little cibucles will kill them.
The best thing on the bottom of a tank is either nothing and a dark cloth beneath the tank, or large river rocks. The frogs tend to kick of and swallow thinsg when they eat.
How big of a tank are you planning on getting? These two frogs will be needing a twenty gallon to themselves with a powerful filter and afew plants, real or fake.
Hope I helped!