Adding light after the fact.

[NewYorkReefer1988]

Hey all, I currently run 2 hydra 26’s (with diffusers) using the BRS modified AB+ spectrum (about 54 watts of power) on a 4 bulb aquatic life T5 hybrid fixture with 2 ATI blue plus bulbs and 2 actinic bulbs mounted about 10 inches high on my 4ft 120 gallon sps dominated tank. I am about to get another hydra 26 to mount in the middle of the fixture and I’m just wondering what the best way to go about adding that much extra light would be.

Last time I took par readings with my current setup I was getting readings of 300-400 in the top 1/3rd of the tank,200-250 in the middle 3rd and 100 to 250 in the bottom 3rd. Obviously there are darker spots but in the center 3/4 of the tank these were the rough readings. (Also took these measurements when my fixture was mounted 2” higher and my intensity was turned down about 15%).

My main concern is that I don’t want to bleach the Corals but I am having some shading issues and a couple bigger colonies eventually died because of the die off from underneath My plan was to just keep everything the same in terms of intensity, pull the fixture back up to 12”, put the new hydra in the center of the fixture, and bump out the other 2 a couple inches closer to the outside. I’m also wondering if I should turn all 3 front to back in orientation or maybe just the outside 2 and leave the center one mounted lengthwise for wider spread? Any help is greatly appreciated!

 

[ndrwater]

I would ramp down the intensity without changing the color spectrum and retest par.
Less is better than more when acclimating.

 

[NewYorkReefer1988]

I would ramp down the intensity without changing the color spectrum and retest par.
Less is better than more when acclimating.

I hear you. I’m really trying to get this done without renting another par meter though. You think bumping down 30% and raising the lights by 2” would be sufficient? Considering that the t5’s would still be at full blast...