mh on a 12g jbj nanocube

[spikehs]

I plan on setting up my nanocube again, as sort of an "inbetween tanks" tank. My plan is to grow out a few select sps to a decent size so whenever I get the chance to setup my new one I'll have some established colonies to put in it. I was planning on getting a 250w pendant, which will work for my next tank... however I'm a bit concerened it'd be way overkill for the nanocube? how high above the tank do you think i'd need it? 12-24" ? Thanks!