[GoinSalt]

I've been running 110W of PC light over my 100 gal tank for the last year. The bulbs are at least a year old.

I just picked up a four-bulb, VHO fixture with four 140W bulbs (2 actinic and 2 10k).

How do I acclimate my lifestock to what will be a DRASTIC change in light?

Also, how high off the tank top should the new lights be?

Thanks,
Nate

[Ninong]

Are the new VHO lamps mounted inside a canopy or are they in a separate fixture that can be raised and lowered? Your new lighting is five times as much as your previous lighting, therefore you would want to raise your light fixture (if possible) well above the water's surface so that the intensity of light reaching the corals is not much more than what they were previously experiencing. Then you would gradually lower the fixture over a period of at least four weeks until it was down to your ideal position.

The ideal position for fluorescent lamps (without metal halides to worry about) is between 2"-4" above the surface (assuming there is splash shield).

In situations where it is not practical to raise and lower the lighting, then you have to resort to other, less desirable methods of achieving the same thing. You could place shade cloth over the tank and then gradually remove it or you could start out with a reduced photoperiod and then gradually increase it.

Ideally you want your new lighting to start out with exactly the same intensity as your previous lighting and then you want to gradually increase it over a period of at least three weeks. Obviously a lot depends on the difference in intensity between the old and the new lighting. In your particular situation, I would err on the side of caution.

[GoinSalt]

The good news is, the fixture is "free floating" right now -- it's a retrofit. The bad news is, I have to now rig up some type of hanging deal

How high should I mount the lights as I gradually lower them? Also, I currently don't have any corals, just fish and LR. I wanted to get the lighting taken care of before getting the corals.

Nate

[Ninong]

You have nothing to acclimate. Just set up your lighting the way you want it. The fish may be surprised by the sudden increase in light intensity but they will get used to it in a matter of hours.