Hey guys.
I've found that the "vivarium" I'm making has somehow turned into a plaudarium

I've changed the plan to have a false-bottom, and just have a small pond area instead. This way I can still house frogs if I want to later on. *dances*
So, I have strategically placed some nice looking river rocks, but I'm wanting a bigger contrast than aquarium gravel. I was thinking that river sand would look great with the larger river rocks, but then yellow flags started going off in my head...
Is it safe to use sand underwater if I want to house grey tree frogs or spring peepers? Both are extremely common around here, and are even becoming pests to one of my friends (she has a very big pool). haha I can help releave her of some of her frogs and have a "free" pet.
I will have a few mosquito fish or other cheep "native" fish in the water area, as well as snails and maybe shrimp. isopods (pillbugs/rollie-pollies) will also be in the tank for munchies. Their main diet would consist of pin-head crickets and maybe wingless fruit flies (for the spring peepers).
Will having a sand bed under the water harm cause harm for these two species of frog? The spring peepers hang around ponds, while the tree frogs live ... well in the trees. The last thing I want is to have them suffer from eating sand with their meals
Also, if you don't suggest using sand, what else would you recommend?
**oh- and I know I cannot/shouldnot use calcium sand. no worries there- I have kept fish before
