How hot?

[rscotth]

1.How hot are 400w MH?
2.How do they compare to 250w MH?
3.Are 400w lights better for growth or just color?

I am planning for 2 MH on a 100 gallon 5 foot long tank with actinic supplimentation. It is going to be a sps dominated tank.

TIA,
Scott

[kevinpo]

How deep it the tank? That and what corals you plan to keep are the deciding factors in choosing between 250 or 400W bulbs. If it is 20" or less from the top of the sand bed to the water surface (IMO/IME) 250W bulbs work very well for growth and color (Acropora sp.). If more than 20" then 400W bulbs will give you the flexibility of placing acros near the bottom resulting in more available real estate.

HTH,
Kevin

[rscotth]

It is 60" long, 20" wide and 21" tall. The frags tand small colonies that I have are doing well under 175 MH in a 55 gallon but the colors are mostly brown. I have: orange Montipora capricornis, green M. capricornis, orange M. digitata, brown M. digitata, green slimer, tricolor stag (now just purple tipped), purple stag (now green), Acropora humulis, A. granulosa, Hydnophora, and a few other Acropora spp.
I an not getting very good growth even though my calcium is 440 and Alk is 13 dKh. The only thing that is doing real well is the Orange cap. I am not opposed to the 250's I just wanted to do what is best without the need of a chiller.

Thanks for the reply,
Scott

[Newreefer]

Good question - How hot are the 400's. Would 2 X 175 Watt MH's be hotter than 1 400 Watt MH?

[reefhead]

Originally posted by Newreefer
Good question - How hot are the 400's. Would 2 X 175 Watt MH's be hotter than 1 400 Watt MH?

No

[kevinpo]

IMO if your house has AC you can use 2 - 250W bulbs and use a fan to provide enough evaporative cooling to not need a chiller. For your size tank 250W bulbs will work very well for 99% of corals to provide both growth and color.

HTH,
Kevin