HQI 150 10k or 250 20k radium

[tendar]

I am setting up a 37 gall sps-clam tank with a 5-6" sand bed and cpr hangon refugium with miricale mud. I am trying to decide which light to use.
Either a 250 watt 20k raduim or HQI 150 watt 10k double ended Halide. The water depth with be only 15" max depth from water line to sand.
With the HQI i can probably set it faily close to the water surface like only 3" inches away. That is guessing that with the housing it wont put as much heat into the water as the 250 20k radium

[Ninong]

So are you talking about one lamp to cover the full 30" length of the tank? If that's the case, you won't be able to position it just 3" above the water because you won't have adequate light spread.

Ninong

P.S. -- The clams would prefer 10,000K over 20,000K.

P.P.S. -- According to Giesemann, the effective light spread of the 150w 10,000K HQI DE lamp mounted in one of their high quality reflectors is 23"x27" with the bottom of the fixture 30 cm (12") above the water.

[tendar]

Sorry the tank dimerensions are 24Lx18Wx21H. The canopy will be 12" high so the light can be any where from 1"-10" above the water.

[Ninong]

OK, that's a different matter. I thought a 37-tall was 30"L x 12"W x 24"H.

Have you given any consideration to a single 250w 10,000K HQI DE lamp? Especially since you are going to specialize in SPS and clams. However, I believe that either of your two proposed lamps would work out OK (either the 150w 10,000K HQI DE or the 250w 20,000K HQI mogul base). It's just that a 250w 10,000K HQI DE would have a lot more PAR than a 250w 20,000K HQI mogul base lamp or a 150w size DE lamp.

Good luck,

Ninong

P.S. -- You will need to adjust your thinking on the position of the lamp above the water or you won't have good light spread. You probably need to figure on about 8" above the water, at least.