MH 2 much 4 90 Gallon?????

I gave back the 400w(borrowed the "grow light") for the 8x54w t5 ice cap retro I bought. It is definitely as bright as the 400w light was. The only difference is its all the way across the aquarium

 

there is noting wrong with the 400w halides on a 18in tank... it is a slight bit excessive but nothing to fret about. what specific kind of corals are you trying to keep?

 

Dingo you think I'll be ok with 2x400 watts in a 48L x 18D x 24H? I want to keep a little bit of everything; Sps, lps, soft coral also a couple clams eventually.

 

Yeah, if you have the ballasts, reflectors, and bulbs there is no reason to buy all new!!!
400w is great for that size of tank and you will get great coral growth (given you have quality lights). Your sps and softies will absolutley love it, your lps will be happy as long as you keep them on the sand bed. clams will be MORE than happy with that

I take care of the display tank at PSU and it is 24 high and 72" long. we have 4 400w ushio 14k and the growth is about a foot or more (depending on the type) a year on each and every coral

 

What do you think about my canopy only being about 8" high. Is that going to be an issue?

 

what reflectors are you running?

 

The reflecters are curved. In a "C" form. Sorry I don't know the specific name.

 

That is probably too low.

I had to raise my old 90g's canopy several inches to get clearance when I had a very low profile MH reflector.
My old canopy was like 8" tall.
You can certainly ligth a 90g with 400watters, but if you use 10k bulbs you might need to pay close attention to where you put lower light corals.

If you have 15-20k bulbs, then that matter is less of an issue.

 

do you have a chiller?

 

I have a 1/10 chiller. Who high do you think the Canopy should be?