Piece of "Cork Bark" siliconed on top of glass/acrylic/pastic which is siliconed to tank. This way the cork gives the slider gripage. Or a Log that touches bottom leaned to the tank (no silicone and it's easy to take out and clean the tank ). Since it's only 18" deep (I'm sure you're not using it full) you can stack rocks so the trutle can come completely out of water (heat lamp above it would be nice ).