My mantis tank is still pretty new so I can only relay my very limited experience. The tank now has been up and going for 3 weeks or so and the mantis has only been in there for a little over a week. I think the biggest and most important factor is going to be keeping the water quality good. So weekly partial water changes to keep the phosphates under control to inhibit algea growth.
On Tues I added 3 turbo snails to the tank, mainly for food but also in hopes that they would survive long enough to take care of a little bit of clean up. Well he took 2 of the snails out the first night....but he's left the third alone. So now I'm hoping he'll leave it be for a while but I think it's just a matter of time.
I had a few patches of green algea growing on some live rock. I'm not sure the type but it was a dense clump of bright green moss. The turbo snail doesn't seem to be doing anything to these patches but to my surprise today the mantis was beating the rock and pulling the algea up. He rolled it up into balls and took it into his den...I guess he uses this for building material. He's also been bashing up all my live rock and using the bits for building material...pretty interesting to watch.
-David