MH distance from top of water...

[X-Treme]

How far do you people running MH lights keep them off the waters surface? My 250w is about 5" off of my 36gallon custom and I get an 8 degree temp swing during the day. Also, now I am noticing green algae forming on the glass (temp related? new tank syndrome?). Should I raise the light? What is the usual distance from the surface? Just kinda curious how others are runnng?

[crystalz]

I have a coralife fixture on legs that keep the light approx 3 or 4" off the top of my tank and I get about a 3 degree change. So during the day I run a fan and it keeps my temp swing to less than a degree. With the 250 you should be able to keep the light approx 6 to 8" off the top of your tank and a fan would probabally kee the temp swing down. A chiller would be the best solution to a temp swing as far as I know. How many hours of light do you give your tank? Do you have lots of inverts ei.snails and crabs and also do you find your skimmer is pulling off alot of skimmate? I think to a certain degree all tanks will get algae on the glass. I have to clean mine weekly, but it's not hair algae.

[j83]

My 250's sit about 6-7 inches off the water. I have a chiller which helps a lot - the best investment I have made! An 8 degree swing is a lot - I could see corals being very stressed out with that. Fish might be a little more tolerant, but it is still a large swing. I guess it also might help to define '8 degree swing'... are you talking 78 to 86? or 78 to 82, back to 78 (4 degree's up, then 4 back down)

Either way, it would help if you added some fans if a chiller is not an option. The less swing the less stressful it is on fish/coral.

[Reefhawk1]

my 250Watt MH are 4" away from the water surface. The glass gets a slight green tinge of algae every few days. No hair algae whatsoever though.

[X-Treme]

The temp swing is 78 to 86 and the green algae is NOT hair algae but it forms on the glass within 2-3 hours of the MH turning on (ie. I cleaned the glass really good last night and by noon today (2 hours of MH) I have a noticeable film of green slime on the glass) I have no corals in there yet, but the 2 clowns don't seem at all stressed nor do any of the inverts. (snails, hermits, shrimps)

[fishface]

Originally Posted by X-Treme

My 250w is about 5" off of my 36gallon custom and I get an 8 degree temp swing during the day.

YIPES! i've got mine about 14" off the water line. but i also have a controller that'll kick a fan in if temp gets too high...or if it gets even more high, then it'll turn off the halides. i'm getting about a 2 degree swing. if you're getting 8 degrees now, just wait till it gets hot...chillers are a fortune.

[Reefer Rob]

The height off the water depends on what reflector you are using. My 3 400Ws with Lumenmax reflectors are 9" from the surface. Winter temperature fluctuation is less than a degree with a controller and fans. We'll see what happens this summer.

[untamed]

I'm a good 12" - 15" off the water surface right now with my 250W halides. That is mostly because I didn't want to shock anything and everything is still relatively new.

I'll probably end up closer to 6" or so by the time I'm done.

[vanreefer]

about 8" with DE 400's I also run a chiller