I'm in the process of upgrading and was wondering how close or how far apart should two MH 250Hqi bulbs be from the t5's. I dont want them to overheat.
I have a Maristar setup that has the T5's reflectors placed right next to where the MH reflector ends (long side). Its been running with no heat issues for the past 2 years or so. Providing you have adequate ventilation you should be fine. As for spacing the MH reflectors apart, I would imagine you would want to get an even spread for your tank so you would space them based on tank obstructions like braces, etc. I've seen folks run ROIII's within 4-5" of each other with no problems.