Hi Andrew
Although I have not set up my new tank yet, I plan to have it heavily planted with a pair of Rotkeil sevs in (plus others), so have no actual experience.
However, this article gives me hope
http://www.calgaryaquariumsociety.com/A ... _Tank.html
So from my research it seems they obv like a good old dig at spawning time so use eggcrate on the base of the tank and secure plants into it so they root under the eggcrate. Find plants they dont llike to eat (there is a list here from someone
http://www.virtualseeds.com/tankmates.html) and feed them on other veggies to keep them happy as suggested above.
I like te idea of keeping a fast growing floating plant that they like to keep them away from other stuff as mentioned above. I did speak to a guy who created a ball of trimmed plants and dropped it into the tank for the Sevs to graze on. He said it worked for him!
Good luck with it, research of their biotope suggests they like to be in and amongst plants, so anything yo can do to give them their natural habitat must be a winner.