light and surface distance

[Vince S.]

My powercompact light is about 3 inches off the surface of the water without any glass tops. is that ok? is ther ea need to put some type of cover over the surface of the wateR?

[eses]

It is personal preference more than anything. I feel comfortable having a sheild of some kind protecting the bulbs from direct spay or jumping fish. I have the "egg crate" light diffuser grating covering my top to keep everything in (and the cat out.) My PC lights are in a ABS hood with a plastic sheild, and are about 2" from the water. This is all hidden by my oak canopy.

Many people just have their lights attached to the canopy with no protection, and seem to have fine results. When I switch to halides, I will most likely do this; I will keep the egg crate, but nothing to sheild the lights otherwise.

[Vince S.]

would having a cover make any differences in terms of evaporation ?

[Venaman]

doesnt the eggcrate reduce the amount of light going into the tank
or is it so small of a difference that it does not matter

[eses]

A cover will help in terms of evaporation, with more of a lid you will have less water escape; but you will have your temperature rise. I've personally found if you cover where water flows, say where it enters your sump, it will help reduce evaporation while letting the gas exchange. You want to make sure you have pleanty of fresh air near your water so you get proper oxygen exchange. You pretty much need to tune it for your specific tank, do what works for your setup. My 29G had a all glass hood, full coverage with only air coming in from the air-gap created by the overflow. But I had no cover on my sump, and a fan under the stand. This worked well, and my oxygen was high. My evaporation was low, and so was my temperature; but I was running low watt PC lights. The same setup won't work with my 75G with halides, it would heat up the tank too much.

The eggcate has to reduce the light some, while the grating is blocking a bit, I think it is a pretty small amount. I do notice it channels the light more, so you get more of a beam effect with the light shining through the grating.