I am not familiar with a 72 gallon corner tank. However, I have a 92 gallon corner setup as a reef tank (SPS dominated), and I use a single 400 mogul socket pendant. I would assume a 250 DE HQI would suffice as long is it placed properly. I think a single 150 DE HQI might work, your carpet plant in front would be my only concern. They would still grow, but I am not sure how well.
I find if you center the MH in the corner side 1/3 of the tank it looks the best. It really stresses the depth (front to back) of the tank. It seems foolish, because the most surface area is in the front 2/3's. It takes a little playing around with to find what you like the best.
However, if you get a 250 you will run into the same problem as I am. There are 3 bulbs I have found, and they are all cheap in my opinion. I assume one of the big names Gieseman, Ushio, Aqualine Bushke will come out with one, because everyone who has a 250 DE HQI would love to have a quality bulb. Not to say one does not exist, but I have not found one yet. I doubt any 25-40$
MH bulb is good. Just my 2 cents.
Last edited by Tuchon35; 02-11-2009 at 04:17 PM.
Reason: Light placement