Question about coco husk substrate

[Pixie45]

I have 16 or so tree froglets and want to know if ive got what they need in their tank.i just got some coco husk substrate and noticed that it sticks to them a bit and im afraid they may accidentally ingest some while feeding.thwy are about 7 week's old.i haven't been able to afford everything they need but I've got a pretty good start.im just new to this and want to make sure they have what they need.i have a 20 gallon tank and I put a large plate of distilled water and some sticks and leaves in there as well.im thinking of removing the husk and getting some aquatic rocks.any advice would be appreciated. Also need to know if tree frogs have to have heat.thanks