at one point in time i slacked off and didnt keep up water changes and was feeding too much. I was also using tap water for top off. i quickly developed a pretty bad case of hair algae. All this in a biocube with LR, LR rubble (in the back chamber), and a bit of carbon.
now my mantis tank is 100% free of the crap just because i feed less (once every three days, remove uneaten food within two hours) and keep up with my weekly 20% water changes. while i was actually trying to get rid of the algae, i did two 20% water changes a week. just had to be careful with fluctuating params. I believe using RO/DI for top off also helped.
for my own battle I didnt bother using any media other than carbon and my good ol trusty LR. I also used three day periods of darkness, but that didnt seem to help at all for hair algae.
another solution might be to just get bigger turbo snails. of course if your mantis is a big aggressive peacock or chiragra, then i think you're hooped there. either way i think water QUALITY control is a much better solution because you're forced to actually address the root of the problem instead of just brushing it under the rug. i mean, all the snails really do is hide the fact that you have the problem. the problem itself is still there though.