MH wattage & depth
 

I'm in the process of setting up a new tank, and can't decide which lights to use. The tank will be a mix of SPS and LPS and is 24" deep. I have a 2X400w MH fixture and a 2X250w MH fixture I can't decide which way I want to go. I have been a firm believer that you can't have enough light over a reef tank, currently i'm running 11 watts per gallon. but with the extra tank, cost and heat are becoming a concern. I thought I would throw up a poll to see what others are using.

I think there would not be a huge difference in heat between 250W and 400W.
heat will be an issue regardless. unless your tank is in the basement.
May be you need to decide what kind of SPS you want and how much light do they need .
Even though i am T5 user; in your situation (you already have the fixures) i would get a good air flow through the canopy and go with 400W+T5 AquablueSpecial (60%actinic&40% blue)for getting super bright colors out.
Just make sure to get a good ballast like M80 and good reflectors all these things are KEY points especially reflectors.
If you look at Web based SPS retailers that is what they use 400W+T5. seems to work just fine.

Andresont
i have to disagree. There is a HUGE difference in heat between the 250 and 400.
Scum
If you're mixing LPS and SPS, i would go 250W and keep the SPS higher up on the rocks and the LPS closer to the bottom.

Thanks for the input guys. I should have been more specific. The 400w fixture is a PFO system and has dual 96w VHO's. and the 250w fixture is a Hamilton HQI and has dual 56w HO T5's. The tank will start off being mostly SPS ( acro's & monty's) but feel that I will start mixing in more LPS as time progresses. I'm not going to get rid of the SPS but I miss the vivid colors and beauty that LPS bring to the tank. I'm not going to get rid of the SPS. Heat has always been a problem for me. I have dual chillers. One for the daily chore of chilling, and one for backup just in case the primary one quits.

Might take a look through some of the Tank of the Month articles for similiar size/shape tank to yours and get ideas what the TOTM people are using.

you missed an option, 250 watt SE bulbs driven by HQI ballasts. suprisingly will give you a higher output than a 400 watt. at anyrate a normal 250 should be good, anything deeper than 24" and I would recomend the HQI 250 ballasts and SE bulbs or the 400's

Steve

Good point. I may as well go that route. I have the 250watt ballasts. All i need to do is put 250watt bulbs in the 400 watt fixture, and run it with the HQI ballasts. More light than the 400's with the power consumption of the 250's. Great thinking. Why didn't I think of that?? thanks.

I see the majority of people are using 250 watt lights. Do you keep the more light demanding SPS? and how low are you able to keep them in the tank? The way I understand it is that 250w is enough light, but penetration becomes an issue. Will high light SPS (acro's) flourish at the lower depths?

I can't seem to find any concrete data on running 250 watt SE bulbs with HQI ballasts. I understand that the light output is more, but can't find anything stating just how much.

you can grow SPS in a 24" tank with 150 bulbs, it is all a factor on what you want your limiting factor to be, food, light, ect.. and yes people are growing them with T5's and they are not even close to the output of a MH, but better than PC or VHO.

Ok, 250 watt is more than enough light for a 24" or less tank, almost all 250 watt bulbs are based off of European bulbs and hence the design is for European power specs, all a M80 ballast is doing is reproducing a European output from North American power input. it is more stable, easier on the bulbs starting and actually drives the bulbs properly, not overdriven. (non of this applies to a so called 400 watt HQI, because there is no such thing)

anyways I ran this type of set up for about 6 years with no problems and increased bulb life (measured with my PAR meter, not a guess) and I was growing out frags on the bottom of my tank no problem. So to answer your question, yes they will flourish with any type of 250 watt set up.

another thing to note is reflectors are just as important as the bulb and ballast combo, My 250 watt set up was putting out more PAR than a Iwasaki 400 watt system, I attribute this to the HQI ballast running the AB bulb to proper specs, and the home made reflector I was using. look at the different reflectors out there and spend the extra 15 bucks on a good one.

be careful of electronic HQI ballasts though as most under drive the bulb. Lately there have been good ones coming out though.

Steve

Concrete data on running SE bulbs on HQI ballasts (or any other type of MH combo for that matter): http://www.reeflightinginfo.arvixe.com/

I have an 18" deep tank running a lot of friggin' light as you can see from my sig. I keep my crocea clam on the bottom no problem. Some of my LPS bleach even down on the bottom so I have to hide them in shadowy areas.

SPS should be placed up high regardless since that's where the wide open flow they prefer is located. Look on any natural reef - the SPS are always located at the reef crest.