I think for my Midas I have found a good balance between what the fish likes and what will sustain the look of the tank without huge holes and piles of gravel/sand. The rocks are from a local river and most all are too heavy for him to even budge. Now that might (doubt it) change as he hits full adult size, but for now it's perfect. The substrate is Flourite which gives the dirty bottom look without the dirt which is the look I am going for, kinda like some flooded woodlands or an edge of the CA lakes. Anyway the pictures below show how ths look stays the same even after he has been digging. The rocks stay in place an he can only go so deep. No more bare bottom craters or gavel drifts up the side of the tank. Just thought I would share my luck with this Midas and his tank. Thanks for looking.