Metal Halide Questions

[howardcu]

I have a 75 gallon reef tank that I would like to get 2 PFO pendants for. My question is about the cost difference between running two 400W bulbs vs two 250W bulbs. I also would like to know if 250W is enough to effectively keep and grow SPS's. Oh and the 2 PFO pendants I would like to get also have 2 28W power compacts each so those would be actinic while the MH would be a 10k probably. There isn't much of a price difference on the dual ballasts or the bulbs, but I was wondering long term if the extra power consumption is worth it. Does it actually make coral grow faster/better or is 400W halides just too much on a tank of that size. Oh and I don't have a chiller, but the tank and sump are in the basement and the light will just be hanging from the ceiling, not enclosed in a canopy.

 

[thegrog]

With your tank, I'd go with the 250w pendants. Unless your tank is more than 24" deep, then the 400s will be overkill. Will drive up your power bill, your tanks temp, and may fry anything close to the surface in a 75.
If you go with 14,000 or 20,000K bulbs, you won't need the PC actinics. The thing is that 56watts of PC light won't make much of a difference against 500 (or 800) watts of MH light.
Keep the pendants, keep the top open, and keep a fan blowing across the water surface if your tank gets too warm. In the summer, my fan is on all day and for an hour past when the lights go out, and only on for 2 hours daily now and all winter. A timer is priceless for this. You'll have more evaporation....but won't have to buy a chiller!

 

[golfish]

Originally Posted by TheGrog
and may fry anything close to the surface in a 75.

I don't think tank size has anything to do with how close a coral is to the surface, JMO..
I agree with TheGrog that you'll be fine with 250 watters...400's would be nice but you'll your going to have heat issues with 250's, 400's will just make it worse.
FWIW, there's isn't going to be that much cost diff running 400's over 250's, we're talking 300 watts for 8hrs...Its really not just about the lights, you have to also consider controlling the tank temp.

 

[howardcu]

I know the temp will be in an issue, that is why everything is in the basement and with an open top. I also have saved a spot for a chiller eventually in the summer months. I was just wondering if anyone had tried 250 vs 400. Maybe I will get one of each and then fragment a few corals and see which side the frags grow the fastest and look the healthiest on. I have also considered the 14k also, it is just I got the PFO's with the PC used at a great price. I agree that 112 watts of actinic compared to 500 or 800 watts of daylight would not be the best situation. I might just go with 50/50 PC and 14 or 15k MH bulbs. Thanks for the input.

 

[golfish]

I've used l...250 watt SE's, DE's and 400 watt SE's....I'd check out Sanjay's lighting web site and see the diff.
I've been running 400 watt bulbs on my current sps tank, I'll soon be switching to 250 watt DE's just for the hec of it...That's something you might want to consider, running 2x250 watt DE bulbs (HQI)