MH's too strong for my tank?

[reef dude]

90 gal Tank is over a year old and had LPS and softies. Been using 2 175w metal halide 5500k bulbs supplemented with 2 40w actinic bulbs. It seems like every time i get a new coral, or ones that have been in there for a while start to shrink up and turn dark in color. My brain coral seems to be ok b/c its on the bottom of the tank where the light is possibly less intense. All of my other corals are on the outskirts of the tank (eg. In caved areas, in the corners of the tank, under cliffs where there is indirect light, etc....) Whenever i move a coral and put it out in the open where it can be directly exposed to the halides, they seem to not like it at all. Is it possible that these corals need less intense light?? Is it possibly to "burn" corals? All i would like to do is have some corals that i can put on my rocks that are in the middle of the tank where you can see them, rather than in the corners. Please help...
corals:
large finger leather
toadstool/tree coral combo
green open brain
alveopora (Caved w/ indirect light)
button polyps (receiving indirect light)
xenia (indirect light)
mushrooms ( at the bottom of the tank)

 

[krunk]

i would have too say its your bulbs...5.5k? That is a horrible color for corals, the lower the kelvin rating, the colors of your corals will get worse.

 

[buzz]

I would increase your bulbs to 10k's, and swap out the NO Actinics and go for VHO's.

 

[reef dude]

I have some 10k's on order. But wouldnt the 5.5k's actually promote coral growth rather than make them shrivel up? ALso my hood is fitted for NO flourescent bulbs, how would i make it take VHO bulbs?

 

[jonthefb]

i would alsohave to agree that the color temp of your bulbs is hurting ore than helping...65K iwasaki bulbs promote coral growth, and with enough supplemental actinic, they would look normal, however 55K are really doing nothing more than stressing the corals out and making them change colors...LPS, and soft corals can really tolerate any amount of light...you just have to make sure its the right kind and that you acclimate them to the light over a proper period of time....
you as a hobbiest need to observe what type of lighting they came out of in their holding tanks at the lfs...if they came out of pc/vho or No lighting, then they are going to have to be acclimated to the increased intensity that you have in your tank, this is really where the term burning corals comes in.....if you acclimate to light too rapidly you can burn your corals and possibly kill them...on the other hand, if the coral cam out of a tank with MH lighting more intense than your own, you would need to start the coral up closer to the light and then gradually work it down to the location you want to keep it in...
i would definately swap your bulbs out and leave the corals where they are for a week then gradually start to work them up in the rockwork over several weeks until you finally get them where you lik!
good luck
jon

 

[dburr]

I agree with jonthe fb. If you are placeing them under MH and they came from a tank with PC, they wont handle the intense light. They increace zooanthely (spelling sucks) and turn brown.
You can use fiber screen also to sheild it from the light. Remove some screen every few days.

 

[attml]

I agree on the lighting issue but also what are your Calcium and ALk levels and how often and what do you feed your Fish/corals?