metal halide lighting


Active Member
i am thinking about upgrading my lighting from T5 to MH in my 75 build. i was wondering, should i use 175 watt or 250 watt. i know i probably sound really stupid asking if i should use the lower watt instead of the higher watt, but im on a very tight budget. will it make much difference if i use 2 175 watt MH bulbs over my 75 instead of 2 250 watt bulbs?


Active Member
2x 175w should be plenty, but 2x 250w would be very nice on that size tank. you might have heat issues with the 2x250w once it gets warmer out, so think about chiller costs as well if you dont have central air or AC to keep the room cool.


Active Member
The difference in heat between the two will probably be negligable, the only issue with 175w MH is the availability of bulbs. A 250w fixture will have a better selection of bulbs but may have a higher cost than the 175w so its up to you both fixtures will be adequete to keep whatever you like for corals.


Active Member
i had two 175watts on my 90 and it was plenty of light.
although i just put a 3 250watt and 4 96 watt pc on my 225 and the light shimmers all over the floor and looks great.
250 watt is alot more common though like stated above.
probably better going that way.
i never had heat issues with any mh systems but mine are enclosed with fans .i dont know about the hang over lights with mo fans around them.


Active Member
175w is easily enough but usually the initial cost savings is all of $20 since the bulbs are about $10 difference if that and 250w ballast being so common are just as cheap and sometimes cheaper than 175w versions. I wouldn't anticipate great montly electric bill saving either but heat reduction would probably be the best reason for going with 175w bulbs.


Active Member
I have tested the temp on a 250w bulb and a 150w bulb and both are 500+ degrees, then I tested the temp of the canopy directly above the bulb my 250w was 272deg and the 150w was 310. I am sure the difference in temp had to do with air flow through the canopies but neither fixture had fans between the tank and lights but the 150w had fans inside the fixture to cool the ballasts.
I don't believe even if a there was a 100 degrees difference between a 175w and a 250w bulb it will make any difference to the water temp of the tank it all depends how much of the heat produce from the bulb is able to make it to the tank.


I vote for 250w. You don't need MH to start a SPS craze. A proper T-5 setup is more then enough. Just becareful if you go with the 250w. Any LPS may need to be shaded.


Well-Known Member
I have a 90g I have 2 X 175 I also have 14K bulbs, At first it was thought that I could't have a choice in bulbs but that is not the case. I can have anything I want. 10K, 12K, 14K and 20K all available for the 175W that I have.
I have two ice cap fans, one in and one far not too much heat...It is not hot weather her in Illinois yet, so I can't say for sure on heat issues.
I like light on my tank but not spilling over into my living room. So it is a matter of personal choice how much light you want. I just want you to know you are not limited on the type of bulbs with a 175W.


Active Member
about the heat issue. i really cant afford a chiller so would the best for me be 2x 175 watt? i am planning on having sps and i want them to grow a lot.
p.s. if i did metal halide, i would build a diy hood and install 2 fans, one on each side.
so here are my final questions.
1. will i have to buy a chiller for my tank if i get 175 watt bulbs and install 2 fans in my canopy? the temp in my house gets maximum 70F
2. will i have just as much growth on the sps with 2x 175 rather than 2x 250 watt?


ok well i just switched from 175 over my tank same as ur when i went to my 125 i went to 250w with 14k and my tank never gets up to 78d so i dont see no difference..


Active Member
tell ya what i have 3 250 watt on my 225 and it shows shimmers all over it looks awesome the 2 175watts i have on my 90 dont even compare.
i have only had the 250 lights for a couple weeks but i swear the coraline is spreading faster than 6 months with the 175's
i added 5 corals yesterday all different and they are all open today.
deffinitly go with the 250's
as long as you air condition the house temp wont be an issue.


Active Member
in the summer, i dont air condition my house often, only when temps get above 85F. would that be ok with 2 250's with fans?