DIY MH Help

[salty321]

Finally got around to registering after lurking in the shadows!

For some time I've been running my 6x2x2 with T8's and a single 250W MH. The hood, a diy affair has fittings for three MH's but being enclosed it was getting two hot, so I finally decided to do away with the hood, make up some new MH enclosures and get all three 'on-line'.

Up until now I have been using double ended MH bulbs from either BLV or AB Aqualine with no cover glass, just the lamp fitting screwed to a reflector mounted inside the hood. It was my understanding that the outer glass envelope of the bulb filtered out the harmful UV, but I have seen a lot of posts saying that DE bulbs must always be used with a UV shield but not SE bulbs but no explanation as to why. I know it is possible to get DE bulbs which just have the arc chamber and no outer envelope, may folk are getting them mixed up? Could someone clarify this a bit, is it all bubs or just some?

As said, I've only been using one bulb due to heat, and it happens to be above a very wide central tank brace, would that have had any effect?

Finally, if I'm to continue using DE bulbs and a shield is recommended for UV purposes, what should I use, plain old glass? Tempered? Thickness?

Thanks!

[noodles9987]

To the best of my understanding, the se bulbs have an outer shield built in to them, which filters out the harmful UV rays. The de bulbs however are much smaller and as a result, they fail to have the outer shield built in to them. Think of a bulb, within a bulb. That's the difference. the se bulbs have them while the de bulbs do not.

non-coated tempered glass is the basic glass that is used on de fixtures for filtering out the UV rays. When i say non-coated, i mean no clear paints that have UV resistance are applied to the tempered glass (as far as I know, there is no UV protection comming from anything other than the glass itself).

If you need a sheild for your retrofit de bulbs, you have a bunch of options. Places like marine depot sell them (for specific reflector housings). And, you could also go to home depot or one of the other diy places and buy a cheap de fixture and take the glass out of that (assuming it would fit). Last choice would be to go to a local glass shop. I have one other piece of advice. Contact aqua medic and ask them specifically about the sheild requirements for their lamps. I have called them before about a ballast question and they are very helpful.

[MeuserReef]

Heres what I did....

The fixtures cost me $6 each at Wal-Mart. Im running 150W DE halides in fixtures that were made for 300W halogen lamps. I took out the halogen bulb clips (which were exactly like the MH bulb clips...) and put in the halide clips just to be safe.



The best thing is that the reflectors are nice and neat and the glass is tempered so it provides the UV protection that you need when using a DE bulb.

This setup has been running for about 2 months now and works great.

Gobble Gobble....

[salty321]

Thanks guys, thats just the info I was after.

MeuserReef, your solution was one I too had though of, but the halogen enclosures I've looked at so far have not been wide enough to accomodate the length of a 250W lamp.

I'll go by a few other electrical retailers and see what else they may have, the improtant thing was the glass.

Cheers!

[5.0stang]

MeuserReef
Is the only thing you had to do was put the halide bulb clips to make it work? are those at wal-mart also? Im lookin to do something similar like that (i like buliding all my stuff) could you show me anything else you did?

[BeanAnimal]

I owuld take a hard look at purchasing purpose built DE MH reflectors that are optimized for our hobby.

A reflector is a fairly complex piece of equipment that must move light from the bulb to the desired focus with AS FEW reflections as possible. Each time the light reflects off of a surface, part of it scatters, either to be reflected (and yet scattered more) from another part of the surface, to the water, or away from the tank. These reflections are parasitic.

Those "hammertone" type reflectors are noce for creating light without hotspots for your driveway. They don't fare all that well as efficient aquarium reflectors where we try to maximize the light in a small focus.

You can check some of Sanjays articles for testing he has done on different reflectors. The lumixmax, luminarc, Reef Optix, and several other reflectors fair VERY well and cost really very little.

Bean