I've made a couple of post here, I have read the forums looking for the answer first but don't seem to get a clear picture. I use to be in SW reefs, have two different MH systems. Both are PFO normal tar ballast type systems, one is dual 250 Watt and the other 400 Watts. I also have three Work horse 7 electronic ballast for VHO lights. I have 12K and 20K bulbs for the MH. I currently have two MH bulbs over a 65 tall tank (same size as a 55 just taller) I have fans in the hood so heat is lowered by air circulation. I plan to sell this setup and move up to a 90 or 120... Question is should I sell the current MH systems and change to a Double ended MH system or scrap MH all together? What spectum is best over all for MH use and would you blend with VHO maybe running the MH for a shorter time by comparison? I'm sure I'll have tons of questions for you as time goes. AH... One thing you should know is I don't have this tank setup in FW yet. I do have enough florite to cover the bottom of a 90 about 3 1/2" - 4" deep. All suggestions welcome!