LouH
02/03/2009, 09:44 PM
I have a 117 gallon mixed reef tank. It is 18" X 18" X 7', and I have an assortment of soft, LPS and SPS corals. My "light needy" corals include some acroporas and a bright green leather. My "moderately light needy" corals include two types of plate-like montiporas, a seriatapora, an anchor choral, and some pulsing Xenia. I have been running two 250W metal halides and one 150W metal halide light over the tank, with the 150W pendant over the center brace where there are no corals directly beneath. All bulbs are 10K in color.
I've been running the 250W pendants about 16" over the tank, and the 150W pendant about 8 inches over the center brace in an attempt to make it's lighting intensity about equal with the 250s. All was going well for a time (good polyp extension and color), and then I decided to move corals around the tank into new locations. I moved one of my bigger plate montiporas out from beneath one of the 250s and placed it under the 150. This new placement was slightly lower in depth than in its previous position. After about a week I notice that this previosuly thriving montipoira was bleaching and losing tissue in a descrete band near its leading edge. In response to this I raised up the 150W pendant a couple of inches in an attempt top give the coral some relief. I'll have to wait and see what happens. Right at the time that all of this was going on, I decided to lower my 250 MH pendants about 1". My Acroporas have responded to that by fading in color and displaying partial polyp extension.
So, what gives? I've been mostly careful with light acclimation. Most of the corals in my tank have displayed decent growth and color in the pase three months. All that has changed are minor changes in lighting intensity, and I added a Blue Linkia starfish. Other than that, all system variables have been ideal.
Could it be that the 250s are too intense for my shallow tank? I'd like to get some opinions.
Thanks
Lou
I've been running the 250W pendants about 16" over the tank, and the 150W pendant about 8 inches over the center brace in an attempt to make it's lighting intensity about equal with the 250s. All was going well for a time (good polyp extension and color), and then I decided to move corals around the tank into new locations. I moved one of my bigger plate montiporas out from beneath one of the 250s and placed it under the 150. This new placement was slightly lower in depth than in its previous position. After about a week I notice that this previosuly thriving montipoira was bleaching and losing tissue in a descrete band near its leading edge. In response to this I raised up the 150W pendant a couple of inches in an attempt top give the coral some relief. I'll have to wait and see what happens. Right at the time that all of this was going on, I decided to lower my 250 MH pendants about 1". My Acroporas have responded to that by fading in color and displaying partial polyp extension.
So, what gives? I've been mostly careful with light acclimation. Most of the corals in my tank have displayed decent growth and color in the pase three months. All that has changed are minor changes in lighting intensity, and I added a Blue Linkia starfish. Other than that, all system variables have been ideal.
Could it be that the 250s are too intense for my shallow tank? I'd like to get some opinions.
Thanks
Lou