Is the UV blocking sheet neccesary?

[stano]

Ok I have determined that glass does not block UV. Now my question is does UV need to be blocked from a Metal Halide? The amount coming off a 175W bulb is substantial, however I do not have any reference as to whether high amounts of UV exist is reef areas (near the equator, crystal clear water, etc..) Is the "UV stabilized glass...etc neccesary to protect the bulb from 'spashing and UV' or just 'splashing'. Does the UV need to be blocked? So the real question i guess is "can i just use glass?(which does not block UV)"

Stano

 

[srbayless]

howdy,

OK, here is my understanding of this. The only time a MH bulb needs a UV shield is when it is one of those double ended bulbs, usually the HQI models. The reason for this is the double ended bulbs do not have an outer glass "shell", which acts as a UV shield on the screw-in bulbs.

The outer shell also acts as a splash guard, but I still prefer to use some sort of plastic or glass sheet to keep any really large splashes from hitting the bulbs.

Hope that helps,

Scott.

 

[Len]

UV shielding isn't neccessary for mogul base bulbs like the 175W versions. It's generally accepted that the only metal halides that require shielding is double ended bulbs. I've used all sorts of mogul bulbs from 175W to 400W without any shielding whatsoever. Analyzing the spectrums of some of the more popular MH used for reef tanks, they really don't output all that much UV-A and virtually no UV-B.

 

[Anonymous]

Ok I have determined that glass does not block UV.

I am not too sure how you determined that.... Only glass that does not block UV is quartz glass, and it is not used in most applications. Even a regular 1/8 inch glass panel will block most of the harmful UV... :?

 

[Len]

Yup, forgot to address that too. "Standard" glass will readily attentuate UV. UV stablized materials aren't necessarily designed to block UV as much as they are to withstand UV radiation. UV coated materials, however, are generally designed for the purpose of absorbing long wavelengths.