T5 question

I just bought a new MH-PC fixture for my 75g reef tank. It has dual 250w HQI's and 260w of PC's. I'm thinking about returning it and getting a 450W T5 fixture instead due to heat issue's. My tank is in my loft and I ran the new light for 2 hours and the lights caused so much heat in the loft it was very uncomfortable. And this was with just the MH's running. My question is will the 450 watts of T5 lighting be enough to keep Clams and some of the more light demanding SPS? If not I may have to jump back down to dual 150w MH's. The heat is not so much of an issue in the winter time, but as spring and summer approach it will become a major issue.
Thanks!

 

Raven, what types of clams are you talking about?
You will do fine with Derasa and Squamosa clams as well as many types of beginner SPS' though I would place the corals up high in your tank and use carbon regularly to keep DOM at a minimum along with your effective skimming!
If you chose to go with a Maxima and/or a Crocea, i would place it high up in your tank and get a 3" size or larger ORA one at that for the best chance of survival!

 

I want to keep Maxima and Squamosa clams.

 

You dont 250w MHs on a 75g. Thats too much intensity in a shallower tank. I wouldnt use anything more then 2x175w MH on a 75. A buddy of mine has a 120g thats 25"s tall and he has 2x175w MH plus 2x110w VHO for dusk to dawn effect and he has huge monti caps and all kinds of LPS and softies. So a 75g is 20"s tall, thats 5"s shorter, 5"s less to penetrate. His montis are about halfway in the tank. So with that working, you should be able to have most SPS anywhere you want in the tank, just keep the high demanding ones closer to the top.

Hamilton Technologies website says it best IMO.

"For tank height 18" to 36" use MH 175W / 24" to 36" use MH 250W / 24" to 60" use MH 400W." The lower tank depth numbers is for high light demanding SPS. Which a 75g is on the lower end of 175w.

But back to the original question. 4x54w retro kits with individual reflectors(300% more light typically) is EQUAL to a 400w MH.

 

I have a 2x175w+2x95w VHO on 110g stock tank that is 20"s deep.

 

You should be ok with the Squamosa especially and place it in the substrate. The Maxima should be placed in your rock work high up in your tank for best lighting and they will bore in your rock work and attach it's basal threads soon enough to adhere to the place where you place it...One word of caution! When you place your clams in a particular place, it is crucial for you to leave them where they are. Don't try raising or lowering your clam as they will stress and may succumb to injury or death!
Also water parameter consistency is key! Try not to have too much variation in water temp., salinity etc.!