Why have 400W bulbs for SPS??


New member
If you have a 24" high tank, need to cover a 24"x24" area, and have sps high and low, why have a 400W MH bulb?

I'm surprised more people aren't switching to the lumenmax elites or lumenbrights for the above type of tank and using 250W bulbs to save money spent on electricity. I'm assuming that you'd also save on the duration that the chiller would run as there should be less heat.

Based on Sanjay's article and some anecdotal experience from other reefers, it appears that 250W lumenmax elites or lumenbrights will give you similar PAR levels. I'm assuming that would translate into similar growth/color (assuming that all other variables are constant).

What are everyone's thoughts on this issue?


Premium Member
I think 250s are what most people use on a 24" tall tank. The ones who opt for 400s might have their halides particularly high off the surface of the water, or just want to keep SPS straight down to the sand bed.


New member
also most people using 400W are also using 20K bulbs for higher PAR values, that you can not get with 250W 20K bulbs


Premium Member
Keep in mind old habits are hard to break. 400w MH lamps have been around for decades, while these new high end reflectors only for a couple of years.

The same could be said for why run metal halides at all with LEDs becoming more and more affordable.

My old tank had 2x400w MHs, when I set it up again it will be with much more energy conscious lighting, perhaps even LEDs.

salty child 79

New member
Of course you can achieve 400w par levels with the 250w bulbs in the lumenmax/bright /arc reflectors.

But would that not mean that the same reflector with a 400w bulb would be that much MORE intense? You see where I'm going with this.

Plus there are a lot of people out there with 36" tall tanks that love to keep SPS in the "caves" of the reef. lol. It's all dependant on what your trying to keep.

I Have had 2x400 in the original lumenmax reflectors (23x23) on my old 150g and it lit the whole tank. And it was the perfect amount of light. 250w bulbs in the same reflectors would have never cut it, and I am sure of it because I had 3 of them before i switched to my 2x400s. lol.

Now with a smaller tank (40g) I only run 1x250w radium in a lumenmax 2 pendant, (along with 3xVHO's). And it works out great.


New member
I'm currently in the process of setting up a 105g that is 30" tall and I'm going with the 400w xm 20k using LumenMax reflectors, instead of the 250w xm 10k I am using on my 75gallon now. The only reason I'm doing so is because I want the achieve a bluer look and a similar par rating like the 250w 10k bulbs.