Metal Halide lighting, What Watt?

[ChrisC1029]

I am looking for advice on upgrading my lighting.
I currently have two 175 W 5.5K MH's with two 65W ultra-actinic power compacts installed in a custom wooden canopy, about ten inches above water surface, over a 105 gallon tank. Tank is 48" long and 28" deep (although with about 4" sand bed, its really about 24" to bottom of water). Also have glass covers to protect lights from splash. In the tank have a mixed reef with some fish, soft corals, and some LPS corals.
I would like to add some "light loving" clams (T.crocea or T. maxima) and probably some sps corals, and hence my need to upgrade lighting. Have considered adding a single 400 W 6.5K lamp to the above setup, although space in the canopy would be getting tight. In this scenario, the 400W would be in the middle, with a 175 W on either side, and would keep the "light lovers" in the middle part of the tank, and less light loving softies on the sides. Or would I be better off replacing the 175 W's all together and put in two 400 W's ,or two 250 W's? I'm a little concerned that the latter options might be too much light for my soft corals. Any thought s would be greatly appreciated.

[3_high_low]

Hey Chris, welcome to Reef Central!

I think you would do well by adding a 400W AB 10,000k lamp smack in the middle of the 175's. It's a crisp white color. Or a 400w 20,000 Radium bulb would offer increased intensity and help lessen the yellowish 5500k look.

Don't forget to take doubled ended lamps into consideration. The 250W DE lamps are comparable in intensity to some 400w moguls.

I think two AB 10,000k 175 W's and one 400w 20,000 in the middle might look, and work, nicely. You probably would not need any additional actinic......The possibilities are endless.

I prefer to stay away from lower kelvin bulbs but many have used them with some actinic supplementation and had excellent results.

Do a search on this website. Lighting has been discussed many times.

Good luck

[SeanT]

I would remove the glass covers as well. Helps to aid in heat dissipation and gas exchange. Ten inches above the water shouldn't be a problem. Mine are six inches above and have had no problems.

[ChrisC1029]

Thanks for your input, 3_high_low and SeanT. I will look at the 250 W HQI DE's, which would be attractive as I understand these are smaller bulbs and space is getting tight in my canopy. Is their output really high enough to put calms near the bottom of my tank though? SeanT, I understand what your saying about removing the glass, but I'd be reluctant to do that with the HQI's due to their UV output. I understand that you could use them in a "mini-pendant" with glass shield, but I don't think I've got enough room in my canopy for a pendant.

[onethumb]

Yeah, I'd be leery of removing the glass shields, too. UV exposure isn't very good for you, if for no other reason. Your critters probably don't like it either.

Don

[Zander]

the last two Tank's of the Month (Sept., Oct.) were "only" using 250w, and they look awesome and have had great growth