Need a wider lighting spread on your shallow tank?

[trido]

I have three fixtures set up on my grow tanks that are roughly 16-18 deep. Because I have removed so many of the optics, I run the fixtures at 100% for both channels. Partly I removed the optics because my ceiling limits how high I am able to hang them above the tank. It has worked out well, Two give great coverage on my 4 foot old 120G ( cut shorter to be a 90) and I use a single fixture over my 30" long 35G. I still get great growth and color from all of my frags.

 

[mcarroll]

I love the experimentation! Just a few thoughts...

You probably don't mind, but there's a strong chance of breakdown or early mortallity of the fixtures running them at 100% all the time.

Without knowing how you picked which lenses to remove, you might consider keeping lenses around the outside of the fixture more and keeping more bare emitters in the center. Those fixtures have a nasty hot-spot - in theory that should help lessen it to some degree.

Using a $free app [HASHTAG]#lux[/HASHTAG] [HASHTAG]#meter[/HASHTAG] or a $15 handheld lux meter (or something better if you are so inclined!) to measure the light at the water surface is an easy way to generate an "intensity map" of your light. Then you could easily visualize the hot spot and probably better-target which lenses to remove to even out the light-field.

 

[trido]

Great ideas.
Running at 100% will definitely require me to rebuild these fixtures at the 2-2 1/2 year mark. the fans get dirty and they have thin little heat sinks.

When I originally removed emitters I was more concerned about a nice 14-20K look on the lights when running each channel at an even percentage. I removed more white optics than blues. I also removed the reds and greens so that spectrum would be evenly distributed through the whole tank. Believe it or not, there really isn't a major hot spot under the lights with this optics set up. I treat my frag tanks just as I would with any point source light fixture and put my lower light corals out away from the fixture. I grow the LPS softies and monties out near the egdes of the tank and all of the SPS directly under the light fixture.

A lux meter is also a very useful tool although after a decade of reefing and blasting my corals with light (used to use 400 Watt MH) I have a pretty good knowledge of all the corals in the hobby. If a new reefer were to try this method. I would not argue with this recommendation.