question about MH lights

giantregal

giantregal

Member
i am trying to figure out what lights to get
these are my chouces
2 250 watt lights
or 3 175 watt ligths
i allready have PC actinic and 10000k lights but i am unhappy with the look of the light it is 350 watts right now
i am trying to figure out if 850 watt is too much? and also whether i should go 20,000 or 10,000 k bulbs
seeing how i allready have 10,000k bulbs and actinics can i go 20,000 MH (i really like the look of the purple light) or should i stick to the 10,000K MH's?
what will it make a difference
my tank has 120 lbs of live rock its 125 gallon 6 feet long 18 inches high, 18 inche wide, it has polyps, zoo's, clams, and some fish :)
would i have too much light with 850 watts of light for 125 gallon? or would it be ok?
stephan
 
nas19320

nas19320

Active Member
Your going to need 3 MH setups to cover that area. Generally a MH setup will cover a 2'x2' foot are adequately.
 
beachbumtx

beachbumtx

Member
850 watts for a 125gal tank is only 6.8 watts per gallon. That is not too much. Consider your tank depth as well. Deeper the tank, the more wattage on the MH bulb you will need. 24" and greater depth tanks need a 400 watt bulb. 18" to 24" depth tanks need a 250 watt bulb. Less than 18" needs a 175 watt bulb. Need meaning at least that much.
Hey light gurus, please correct me if I was wrong.
EDIT - Poor use of words. Didn't sound correct.
 
beachbumtx

beachbumtx

Member

Originally posted by GiantRegal
ok then would 3 175's suffice?
and what about the Kelvin?
At least 10K, but 20K will not hurt either. I prefer 20K myself. I love the moving water reflection it creates. Not sure if the 10K does that too.
I have a 20K blue (400watt). I love it.
 
nas19320

nas19320

Active Member
What are you trying to keep? 3 175's will light the tank but you'll get much better growth and color with 250's or 400's. K is mostly personal choice. I'm not a big fan of most 20K's because I don't like the blue look. If you go 175's then I definelty would not go 20K.
 
giantregal

giantregal

Member
ok so ill get 3 175 20k bulbs to go with my PC's
i have 2 36" hoods that have flourescents in them can i take the blubs out and use the hoods to mount the halide's with reflectors in them?
i was thinking about puttin on on each corner and one in the middle of the two hoods (basically 2 in one hood 1 in the other)
would it melt the plastic?
what would be the best way to keep my water from heating up?
should i drill holes in my wood canopy and install fans?
stephan
 
giantregal

giantregal

Member

Originally posted by Nas19320
What are you trying to keep? 3 175's will light the tank but you'll get much better growth and color with 250's or 400's. K is mostly personal choice. I'm not a big fan of most 20K's because I don't like the blue look. If you go 175's then I definelty would not go 20K.
why not with 175's?
i am trying to keep zoo's polyps and clams, i might get some hard corals later but mostly softs, and polyps and stuff :)
 
nas19320

nas19320

Active Member
I guess it depends a lot on what your planning on keeping but it has been my experience that 175 20K bulbs are dim and your PAR values will be low. You'll get glimmer lines regardless of what K bulb you use and MH bulbs get hot.
 
giantregal

giantregal

Member

Originally posted by Nas19320
I guess it depends a lot on what your planning on keeping but it has been my experience that 175 20K bulbs are dim and your PAR values will be low. You'll get glimmer lines regardless of what K bulb you use and MH bulbs get hot.
ok what can i do to keep them from heating up my water?
i will see if i can get 250's since i really want 20k blue light
 
beachbumtx

beachbumtx

Member

Originally posted by GiantRegal
ok so ill get 3 175 20k bulbs to go with my PC's
i have 2 36" hoods that have flourescents in them can i take the blubs out and use the hoods to mount the halide's with reflectors in them?
i was thinking about puttin on on each corner and one in the middle of the two hoods (basically 2 in one hood 1 in the other)
would it melt the plastic?
what would be the best way to keep my water from heating up?
should i drill holes in my wood canopy and install fans?
stephan
Fans for cooling is a must. Don't use the other light hoods. THe bulbs will get hot enough to melt the plastic. I made my light hood out of a sheet of aluminum. With MHs, aluminum should be used for the fixtures. I suggest to buy the already made light fixtures for MHs if you don't think you can make your own.
Other option for cooling is a chiller, but those are pricy. Still may need it if you can't get enough air circulation in your canopy.
Consider the other comment about not recommending 20K for 175 watt bulbs. I don't why it was suggested, but I can't argue otherwise as I am still learning myself. I would like to know as well.
 
giantregal

giantregal

Member
ok
so ill make my own hood form sheet metal thats easy not bad, i can mount them 5 inches from the glass which ends up beign 6 inches from water, i can put fans on the hood, as well as on the canopy
would that be enough?
 
beachbumtx

beachbumtx

Member
On my 20 gal frag tank, I have a 400 watt MH above it. It is currently sitting at 18" above the water surface. I have a fan blowing across to keep the water cool and move the air between the light and water. This weekend I will experiment to see if I can't low the closer to the water and still maintain a constant water temperature. I want to encourage as much growth as possible, so I want the corals to get as much wattage I can offer them without overheating the tank.
 
beachbumtx

beachbumtx

Member

Originally posted by GiantRegal
ok
so ill make my own hood form sheet metal thats easy not bad, i can mount them 5 inches from the glass which ends up beign 6 inches from water, i can put fans on the hood, as well as on the canopy
would that be enough?
What is your tank depth? Will you be able to do your maintenace to the tank with the lights there and running? Will water be able to splash up and touch the bulbs? The latter question is something to really consider.
 
giantregal

giantregal

Member
18 inches of depth
i was thinking of doing something i just saw in someone elses aquarium
bolt them to the top of my canopy door and put about 4 fans across the back of the canopy

by putting them there there is no way that water will splash them, but when i do maintenece the ligths will not completely flash on teh tank, but the PC's will
 
beachbumtx

beachbumtx

Member
Also, if needed, you can alway shut them off for maintenace. Just remember, and I didn't realize this the first time, that you will have to let them cool before turning them back on. They will blink on, then off (like if they burned out), if they are not cooled. Give them 10 minutes or so to cool them turn them on and they will come on as normal.
You can keep your PCs on during maintenace.
 
giantregal

giantregal

Member
well i found my calling
3 250w metal halide's with everything for $340 new
they have 10000k or 13000k should i go with the 13000?
 
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