Using MH only for lighting - add PC?


Plant Guru Team
Lifetime Member
Sep 23, 2007
South Florida
Hey all,

I am currently using a Current Outer Orbit 3x150w 6500k 72" metal halide fixture as my only lighting for my 180. They are hung 9-10 inches above the surface and are one for 9 hours per day from 1 p.m. - 10 p.m.

I see from many threads that folks like to use MH in tandem with other lights, say PC or T5 or something like that. I know Tom's Starfire 180 uses a mix as do many others.

Due to my schedule, I don't get to see my tank much (is why the 1-10), so would like to have a longer duration, but do not want to use the MH to do so.

I was thinking of getting 4x96 watt PC fixture to go along with the MH. The new fixture would be used for the majority of the duration, with the MH now used in a 3-6 hour burst.

So, the new fixture needs to be sufficient to drive decent growth while I play with the MH.

I also want a greater spread over my tank, as the MH does leave some dead spots.

I also want to slow the growth a bit, as some plants grow 2-3 inches a week and I always seem to be in there pruning........

Before I spend $ on another light, or a new one, I would like a few opinions on the following:

1. Does anyone else use only MH for a larger tank? If so, what is your config and setup? Duration, etc.

2. Will 4x96 watt be sufficient for most plants without the MH? I am dosing EI and auto c02. Remember they will also be hung at the same height as the MH. Or can I go with a different config?

3. Would I be better of buying one new fixture with PC and MH combined? I can
always sell my other fixture I guess. Or just a new PC fixture?

I can fit both on my hanging mechanism, but one will be behind the other, no matter which comes first......

4. Can the MAJORITY of fixtures (assuming the bulb pin config is the same) be swapped for a better bulb? I see some fixtures I like but they always have actinics in them and I would like to switch them if so.

5. What seems to be the consensus for temp on these bulbs? I see folks use 5600k, 6700, 8k, 10k, etc. I was thinking of 8k or less.

Thanks in advance to all.

Tom Barr

Staff member
Jan 23, 2005
I do pretty well with either.

I like options etc, but some of the best tanks had only MH's I've done.
Still, that can be done with both. Just stop using the PC's, some go the other way and like lower lighting.

Tom Barr