mathias999us
01/10/2009, 01:16 PM
Bear with me here if you can, a bit of background...
OK, so I have this 8" high tank with 54W T5s over it. I've always thought there was too much light over this tank, because the corals don't expand as full as think they should, and because I find they are lighter and more pale than they probably should be. All the other measurable params on the tank are always.... GREAT. I can list them, but I know the difference between good and bad water quality params, so this has always lead me back to suspecting the lights.
I used to run 4 54W T5s with individual reflectors on this tank. I had a mishap in the tank at the beginning of October where I had to temporarily drain the tank, and move all the corals to an adjacent tank that is deep and has very low lighting. I thought the corals would be quite shocked from this, but to my surprise they were more expanded and healthy looking than ever! They remained this way for a while even after I put them back in the main tank, but slowly returned to the less-expanded and pale look within a week or so. I cut back to only two bulbs after this with some modest improvement in the corals, but still not as much as I thought there should be. I've played around with removing one or the other or both reflectors since then, adjusting the photoperiod, etc. Nothing seemed to make as big of a difference as when they spent some time in the deeper, low-light tank.
Today, I decided to experiment with light distance above the surface of the water. Usually the bulbs are 2.5" off of the water surface. I propped the canopy up halfway, which moved them to 5.25" of the water surface. I am observing a near immediate positive reaction from the corals. Within one hour, they look more expanded and full than they have in the past two months.
So, I think I may have a solution, but I want to understand why. This can't be as simple as "moving the lights further off the water reduces the intensity of the light delivered", because I tried removing reflectors when they were close to the water without nearly as much as a positive reaction. I don't understand why increasing distance from the light source is any different from adding/removing reflectors/bulbs from the light source? Any ideas on this?
I'm going to try to borrow a PAR meter from someone in my local reef club, but I suspect this may be more complicated than simple PAR readings.
Thanks for your help,
Mathias
OK, so I have this 8" high tank with 54W T5s over it. I've always thought there was too much light over this tank, because the corals don't expand as full as think they should, and because I find they are lighter and more pale than they probably should be. All the other measurable params on the tank are always.... GREAT. I can list them, but I know the difference between good and bad water quality params, so this has always lead me back to suspecting the lights.
I used to run 4 54W T5s with individual reflectors on this tank. I had a mishap in the tank at the beginning of October where I had to temporarily drain the tank, and move all the corals to an adjacent tank that is deep and has very low lighting. I thought the corals would be quite shocked from this, but to my surprise they were more expanded and healthy looking than ever! They remained this way for a while even after I put them back in the main tank, but slowly returned to the less-expanded and pale look within a week or so. I cut back to only two bulbs after this with some modest improvement in the corals, but still not as much as I thought there should be. I've played around with removing one or the other or both reflectors since then, adjusting the photoperiod, etc. Nothing seemed to make as big of a difference as when they spent some time in the deeper, low-light tank.
Today, I decided to experiment with light distance above the surface of the water. Usually the bulbs are 2.5" off of the water surface. I propped the canopy up halfway, which moved them to 5.25" of the water surface. I am observing a near immediate positive reaction from the corals. Within one hour, they look more expanded and full than they have in the past two months.
So, I think I may have a solution, but I want to understand why. This can't be as simple as "moving the lights further off the water reduces the intensity of the light delivered", because I tried removing reflectors when they were close to the water without nearly as much as a positive reaction. I don't understand why increasing distance from the light source is any different from adding/removing reflectors/bulbs from the light source? Any ideas on this?
I'm going to try to borrow a PAR meter from someone in my local reef club, but I suspect this may be more complicated than simple PAR readings.
Thanks for your help,
Mathias