Watts per gallon question

Hey everyone I've been away from the hobby for a couple of years and am getting back into it. I'm starting a 75 gallon reef tank with a 30 gallon sump. I found a combo metal halide and t5 fixture for a reasonable price on eBay it is 716 watts with 2 250 halides and 4 t5s. Is this too much light for this tank the mounting legs put it 7 inches above the water. Any advice would be great thanks

 

In a word, yes. You could run just the T5s with good bulbs (like ATI), and that alone would be plenty of light for anything you want to keep in your tank.

Here's a perfect example:

http://www.3reef.com/forums/show-of...as-palys-4-23-13-a-81680-195.html#post1474353

 

Could I run the t5s for the full photo period and just run the halides for let's say 6 hours a day? The fixture is the right price and I want to have more light than not enough just don't want to cook everything.

 

It will work fine for you. Watts per gallon is really an old theory that has really gone out the window with t-5 and MH. It is a lot of light but certainly not overkill.

 

Imo you can not over due the lighting. The sun provides way stronger and harsher intensity than we can ever hope to emulate. My main concern for you would be keeping the water temperature in check. I have seen tanks show better results under MH with t5 than something strictly running t5s.

 

This is categorically incorrect. You absolutely can overlight a reef tank, especially so if you do not photo acclimate corals properly.