Lighting problem.

Ok, I have a 150 gal reef tank with a few acans, a brain, a duncan, green stars, frogspawn, Leather, torch, a Clam, montipora, acropora, some zoo, and a *crap load* of purple mushrooms(yes that is my technical term).

I was running some generic 2x 15k 250 watt metal halides (generic ballast) and 4X 65 watt Power compacts everything was fine untill the bulbs got old and turned blue-white(~1 year old). Some of my corals began to not feed and shrivel up. (water parameters were good and the change wasnt sudden). My tank is 30 or so inches deep so I keep the lights about 4 inches above the tank

I had a little cash in my pocket so did a little research and found out that 10k's have higher PAR and that XM was a good brand. I also invested in 4 new super actinic 65w PC and the 2 XM 250 w. It was expensive but I figured that it would be worth it(coral growth and all).

It turns out that the new halide bulbs are so bright that I need to wear shades to look at my tank. I started off running them only an hour a day and slowly increasing. Most of the corals hate the new lights and a couple of the were about to kick the bucket. The mushrooms and frogspawn "Love" the new lights, they cant get enough...

Before I lost half of my corals, I tried to raise and lower the lights to no avail. I decided to give up, I turned off the metal halides and decided to only run the super actinic PC's. At that precise moment, my corals returned to life and are currently thriving/recovering for over a month.

What the hell? This contradicts everything I have ever read in a lighting forum. I have a 30 or so inch deep tank and I keep all of the good ones at the bottom. they are growing and thriving on PC's alone. Even if I have to change the PC's every 6 months (the recommended hours) I will still save money on electricity and halide bulbs. ( I run my lights ~9 hours per day)

Can I keep my Corals Happy with PC lighting alone? Should I try to work the halides for an hour a day to supplement them? Or is this some kind of short lived recovery phase from all of the light abuse???

 

will0417

The change in color temp and possible much higher PAR from the new lamps versus the old lamps that where in , may well explain why the corals have closed down

does your lamp have a UV shield? as I have read stories (The Kingfish) relating to corals being burned under a new lamp that did not have a UV shield

have you tried screening? you get that black screen from home depot and make 4 layers of it to cover your tank
run the lights a few hours each day, and then next week, remove 1 layer of screen

this helps the corals to gradually acclimatise to the new lamps

I have never tried keeping any corals under just actinic lighting, but IMO I dont think its something I would want to do long term as you stated, it goes against everything we have been taught in terms of a corals lighting needs

Steve

 

Thank you for the response. Yes I have UV shield on my halides and I also have my glass covers on my tank. I really like your idea about using screen to acclimate the corals. Do you have any thougts on height from water?

 

thank you - but I cant take credit for the screens idea, many people have used this method before I became aware of it

MH height above water level

IIRC - it used to be start at about 12 - 15 inches above water surface and then bring down by 1 inch per week, until you get to 8 - 10 inches above water surface

but hopefully someone who has upgraded more recently will clarify

screens - they would just be placed on top of each other, directly on your tank cover
and start with 4 - removing 1 each week at the end of each week until all are gone

Steve