MH and Clams


New member

I am looking to upgrade my lighting to MH so I can keep clams and sps. I have a 29 gallon (30x12x18) reef (actually 14" from dsb to water surface). I will likely use two of my 55 watt pc's bulbs as actinic suppliment along with the mh.


1) Would a 175watt mh setup be more than adequate to keep clams and sps striving in my tank?

2) Would a 250 watt mh setup be too much light for my soft and low light lps corals, and create heat and evaporation problems that the 175 would not?

I want to get what will be best for all of my inhabitants. I would like to go with 250 so if I upgrade later I can use the same light setup, but I am concerned that the lower light corals will not be happy with 250 mh on a 29 gallon tank.

Thanks for any advice.:bum:
A 175 W MH would be more than adequate. You will have to mount a 250 higher up to keep it from heating up your tank.
Make sure that your hood is well ventilate. 29g is not much and will heat up considerably when you put the 175 or 250 W on it during the day. Your tank will be significanly warmer when the light is on unless you have some way of getting rid of the heat effectively.
Thanks, I really respect your help.

I have a six inch desk fan that is setup to turn on when the lights turn on. It keeps my tank almost too cool right now, so I think it should do the trick.

Besides the heat/evaporation issue, do you think the 250 watt mh setup on my small tank would putout too much and too intense of light for my lower light corals? I would like to get the 250 setup, but at the same time I don't want to upset my corals with too much light, and I would rather not have a canopy that is 14"+ high.

The tank is 30" wide, a little longer than the recommended 24" of tank length per each mh bulb, so the edges will receive a bit less light than the center. But I am not sure how much less.
If you do a pendant, you will have no problems. I have a 175 watt pendant over a 15 now with literally no heat fluctuations during the day. I did remove the acrylic splash shield once and the temp did go up 2.5 deg. My maximas are putting down 1 cm of shell a month, the SPS are keeping GREAT color and growing at a wonderfull pace :)

I recently aquired a 29 gallon tank and found another dirt cheap 175 watt pendant, so I'm going to to a 2x175 over my 29. :) The bell shape pendant really focus the light in a narrow spread, so it looks VERY nice...again...more heat from my 55 watt PC actinic then the halides :)

If you do 1x175 over a 29, you will want to take reflactors/mounting into consideration. Also, be very careful what you place on the sides of your tank. A single MH bulb (even with a great reflector) won't put out much PAR on the edges of that 30 inch tank Keep the clammies and SPS towards the middle. :)
Thanks peabody,

Unfortunately I am not allow to hang a pendant from the ceiling. My better half would not be fond of the look, and wants a canopy if I go with MH.

How high would you think I need to place the mh/pc setup to get halfway decent light to the edges? Not enough for clams and sps, but for low-med light corals.
That's a good question. Well, if you need to have a canopy and no reflectors, make sure the bulb is at least 6-8 inches above the water to avoid being splashed! If I was in your situation I'd really study the reflector study in last months by Sanjay Joshi. That should ggive you a good idea about what reflector would be ebst for your tank.

The sides may be a little dim compared to the center, but it will still look OK. But, the PAR won't be good for acros and maximas at the side. Good place to

best of luck!