They've been on the dirt for over a year. I tried them on gravel, but they hated it. The reason I did the set up like that was because when they were in a mostly water - part land set up, they spent all their time on the land. Even now, they spend most of their time hanging out on the bridge or in the plants. There are actually two ponds in there, the second is just shaded over by the plants so its hard to see in the photo. It is directly in front of the pot cave, so when they want to rest in the cave they won't be too far from water. I also clean them daily, so they stay pretty. The light is one of those day light bulbs - it produces a small amount of heat, but mostly just lights up nicely.

Edit: I meant to say three ponds, not two.