How high should lights be off the water?

[customclimates]

2X250 ( 4’ ) Maristar fixture is about 10 ½ to 11 inches off the water. Do you think I should lower it? Always had it this height due to canopy but I am thinking of altering the canopy in order to lower the light fixture. What do you think? Running 14K's...

 

[chew*]

If your temps are decent the more par the merrier, however the lower the fixture is the more concentrated the beam is based on the size of the reflector. Smaller reflectors need to be higher for even distribuition, larger can be run closer with a better distribution of par. Now you see why i'm using lumenarcs.

 

[customclimates]

If your temps are decent the more par the merrier, however the lower the fixture is the more concentrated the beam is based on the size of the reflector. Smaller reflectors need to be higher for even distribuition, larger can be run closer with a better distribution of par. Now you see why i'm using lumenarcs.

I also saw the results….This is why I am asking about lowering my fixture. Anybody else have a Maristar for a reference? Very happy with the tank I purchased but with the overflow in the middle left side of the tank there is a shadow I would like to rid of.

 

[customclimates]

Notice how dark the left side is by the Tunze...
View attachment 31585

 

[chew*]

Yah i had that problem with my koralia 4's, that's one of the reasons I ditched them for the ecotechs. I think I know a way to shed some light in there. I'm getting a hold of some highly polished reflectors from a buddy, Im going to cut them up and line the inside of my canopy with them to get more reflection in the tank. I believe i'm getting quite a few of them. If he comes through for me your welcome to some.

 

[customclimates]

I think it is the overflow that cast the shadow. If I lower the fixture I can light that area.

 

[chew*]

I don't see why not. If you switch to 10k's might be an issue though, I'm screwed if i change to 10k's. Will take like over a month to acclimate them.

 

[chew*]

I think that most people run 8" the lowest. From what iv'e read. No clue as to why, my guess is heat.

 

[Crib]

I have my Maristar 250w 10K 9" off the surrface.
just changed my bulbs, and I can see the growth starting....

 

[Dave McReeferson]

I was running a full sized Lumenarc III ~3" off the water in the last tank (10K XM 250's) without problems. A couple of Acro's and a Monti were only about 1-2" under the surface of the water too. I think it is really a matter of the spread of the reflectors in this fixture more than anything else, as long as you get the light coverage you are looking for then there shouldn't be a problem. Just lower it a bit at a time and you should be fine.

Edit: After looking back at your pic, I don't really see too much mounted up high, and nothing seems to be right at the water's surface, I wouldn't be too worried about dropping your fixture a few inches.

 

[customclimates]

I think I am going to modify my canopy in the morning so I can lower the light in small increments.

 

[Yaktop]

I run the lumanarcs as well. I always heard for MH to run the bulbs 9 inches off the water so depending on the type of reflector that could mean different fixture heights off the water. keep in mind depending on your top surface flow and the type of fish flipping you may have will dictate how clean those reflectors are kept with salt splash. its all a balance IMO. Water clarity is also a key ingredient, if your water is super clean and clear you can get away with more height off the water.