H37 ballast. i ran these on my tank. H37 is a mercury vapor ballast.
also, when you purchase the bulb, make sure you get the one designated 41-R. it's their "reef" bulb and burns a bit whiter to the naked eye.
yes, it'll run on an electronic ballast but much like how M80 ballasts overdrive SE MH bulbs, the H37 ballast will do the same for the eye bulb.
it's not a pretty color, even with actinic supplementation. if there's any yellowing in the water, the bulb highlights it a lot.
as far as growth is concerned, granted i kept the lights with shrooms during cycling and have since changed bulbs, but these shroom grew to enormous sizes. i had 1 hairy mushroom on a piece of rock that was no bigger than 1/2" in diameter and it blew up into a colony of 6 now (after 4-5 months) with the largest mushroom being 2 1/2" in diameter.
i don't know about SPS but if PAR is really that important to growth rates, i'd expect this bulb to surpass every bulb because it does have the highest PAR rating of all the SE 250W (except for XM 10ks w/ M80 ballast vs iwasakis w/M80).
IMO, you want a balance of color and growth. i believe 14k bulbs (or 15k bulbs) achieve this the best.
