MH height Question.

[Twisted-1]

Why do people say to keep a MH light about 8-12 inches off the water. Is there an actual reason to this or is it just a preference thing? I know they get damn hot and heat up your tank but is this the only reason or do they have bad effects on your fish/coral from being to close?

[shotzee]

Its mostly just for heat reasons. It is also sometimes so that you can still look in for a top view of your tank which is always nice to see.

Another thing to consider is the light dispersion the higher up you have your lighting (unless its in an enclosed canopy).

[Aquattro]

Any water splashing on the bulbs could cause them to explode, or at least crack. If they're higher up, less chance of splashing. And heat, light spread, all factors to consider. I have seen bulbs 6 inches away though, and they work fine.

[TheReefGeek]

For all the reasons mentioned, and to be able to work on the tank easier. My next canopy will be on pulleys so I can pull it up and out of the way when working on the tank.

Also when you are upgrading lighting, you should start with them higher up and slowly lower them over time to allow your corals to adjust.

[mark]

Sent a e-mail asking about height to PFO describing my tank and stating was planning on using 2x250W MHs, bottom of my pendants are at 6" based on their suggestion. With the pendants (DE bulbs) there's a glass cover between the bulb and the water.

[mr_alberta]

Also with the lights higher you get a wider spread, but a reduced PAR.

[Kryten]

My next canopy will be on pulleys so I can pull it up and out of the way when working on the tank.
That's a good idea.

My thing about having lights above the tank is that there is so much light spill into the room, which I really don't like. Not too much of a problem for me since I'm not using MH..... yet....

[TheReefGeek]

Yeah, definately a tough decision between a closed canopy with no light spill but potential heat problems, vs. a hangin unit and having light spill.

My solution was building my tank into a wall :)