Lighting Decisions

[dwindles]

I am setting up my 90g tank, and ultimately plan on having a reef setup with l/r and l/s. The tank is 24" deep with about a 4" sand bottom. I plan on building a new canopy with VHO and MH. I am planning on Icecap actinics (4 bulbs ultimately) and 2 MH lights. I am unsure which MH to choose. I will likely get a PFO ballast, and am considering the 175w 5500K lights vs. the 250w 6500K/10K lighting. Right now I am unsure which corals I will be collecting, and I know stronger light is usually better, but I am also concerned with heat.
How yellow is the 5500K light vs 6500K, and does it even matter with the added VHOs?
If I did get the 175w lights, would that be enough total light for soft and hard corals?
If I get the 250w lighting, would heat be much more of a problem, or about the same as the 175w?
Thank you in advance!

 

[mr . salty]

The tricky thing with a 90 is that it is a relativly small tank,,,but pretty deep.So because of it's depth,some will say go with the 250 watt MH.But I dissagree.Two 175's will be fine.Just put the more light"needy"corals closer too the top of the tank.I believe that two 250"s over that tank WILL cause excessive heat problems.As for the K-value of the bulbs,With the VHO blues you will have the 55k should be fine.Although they are pretty much yellow,the VHO blues will more than compisate for it....You will need a cooling fan in there somewhere though.Even the 175's will produce alot of heat.But with a fan,it will not be a problem...

 

[dwindles]

Thanks for the reply! I think the 250w MH may give me more options in the future, and I probably will get a chiller at some point to help control the temps. Thanks for the input.