I just transfered my Cobalt blue sling into a plastic canister (1-gallon) and there's at least 8" of eco earth substrate. I made sure to pack it down well, then saturated it & packed it down again and let it sit for a bit and then poked my finger into the substrate to make a hole for him to burrow but it keeps collapsing on me! Am I using the wrong substrate? Other than my cobalt not burrowing, he's eating very well! I've had him since this past March. Any helpful suggestions/hints would be appreciated!