Metal Halide Lighting Questions

[nkd5024]

I currently have 2x 250 watt metal halides running 14K Phoenix bulbs over my 75 gallon mixed reef. Over the past few months I have been slowly raising the lights by an inch every few weeks as the light is too bright to keep even the higher light demanding corals more than half way up the tank.

The MH pendants are currently 14" above the tank, so I am trying to think of other options to lower the light output enough to be able to raise a lot of my corals up in the tank and get darker coloration from them.

I don't want to shell out the money to downgrade to a new 150 watt ballast and bulbs, so I was thinking that I could possible put a type of glass that only allows a certain amount of light through, in place of the clear UV protection glass I have covering the pendants now. Would this be a viable option, I'm just not sure if preventing light from escaping the pendant would be a bad idea (maybe increase heat)

Or would it be a lot easier to just switch over to 20K bulbs?

Any help is greatly appreciated,
Nick D.

 

[coralnut99]

You'll face the issue when changing old bulbs too. What some folks do is place a few layers of window screen over the tank and remove a layer at a time, maybe every week or so, monitoring corals' reaction.

 

[nkd5024]

Surprisingly enough, when I changed out my bulbs last month, I didn't do anything special, just changed the bulbs and kept the same photoperiod and everything and I didn't notice anything like bleaching or colors lightening up.

I have been debating switching over to 20k bulbs to get better coloration out of my corals. I know the growth rate is decreased in 20k bulbs, but honestly by how much? Does anyone know off hand?

Most of my corals are still frags, so growth rate is kind of important to me atm.

Now, I know that you are supposed to slowly raise corals in the tank in small increments. How slow exactly are people talking about. When I've tried to move things up, I usually leave them at each location for a few day to a week before moving them up. Is this too fast? Should I let them alone for a month or so before trying to raise them?

I also think a lot of my problem is that a lot of the frags I get are from Thatfishplace's coral tray, which is lit by Blue LED lighting only, and rarely sees white lighting, as they keep the Blues on there to show off the frags fluorescents. So when I move them into my tank under 250 watt halides, I can't even keep the acropora frags above the sand bed. So do you think that maybe it isn't so much that my lighting isn't too bright, just that I need to acclimate my corals to higher lighting slower?

Thanks for your input guys!

 

[tiffyreefer]

+1
I did that when I went from 175's in an all in one fixture to 250s in LumenMax reflectors. My corals would have needed sunblock if it wasn't for the screen!