weird question, but I have a trio of "Texas Barred" tigers. They have been happily co-existing in their new tank for about 3 weeks. I can't seem to locate feces, and I've read they defecate a lot. The substrate is coconut fibre mixed with organic topsoil. I'm used to keeping lizards and was expecting more defined poop. It almost looks like I don't need to clean the tank? There's no smell either, just that nice "forest dampness" aroma...