Light Acclimation Advice

[Clamaholic]

I just did a major light upgrade to Metal Halide (2x250 de+2x54 T5 actinics from 4x65 PC). I am presently trying to acclimate my tank to the new lighting. I have a 55 gall with 2 Digi's, 2 Caps, Pocillipora, Lps, Shooms, button polyps, zoas, and a 3" Deresa clam.

I have the light 12" above the tank with 6 layers of nylon screening over the tank. My question is that everything is doing fine except the clam I can only keep the halides on for 2.5 hrs at which point the clam starts reacting badly, gaping, shrinking mantel, closing up. Does this seem reasonable, one person told me with the screening I would be able to keep the light on for the full photoperiod.

Any advice and experience with acclimating clams to lots 'o' light would be great........

P.S. Halides rule!!!!!!!!!!!:bum:

[The steven liu]

I guess you can gradually move them towards the top of the tank with your existing light, and then when you install the new light you can move them to the bottom of the tank. Also reduce the photo period of your new light and increase gradually over time.

[mbbuna]

if you need to cut back the photoperiod also then do so, even with the screens. keep it at the shorter time until everything gets used to the lighting, then slowly ether remove a screen a week or add a 1/2 hour a week until you get it to where you want it, let everything in the tank be your guide, if anything looks funky then stop, even back up if you need to. going from PC's to 2-250w MH is a BIG jump and will take some time.