Glass under MH

[donm]

First I would like to thank all of you for
the information you had supplied me about skimmers. I just purchased and set up my new Prizm. It works great! I'm glad I listened to all of you.
With the purchase of my new skimmer, I also purchased a 175wt MH. My new project is to build a canopy. Is glass utilized under the
canopy(over the tank) to protect the bulb and help out with evaporation and salt creep?
Also what height above the water level is the norm or close to the norm?
thank you all....
Murphy

 

[wallda]

I have glass on all of my tops. I once saw a home that had a 55 gallon reef with no top, just lights hung from the ceiling. It was there 6 years. Well after draining the tank and pulling it away from the wall the owner knew she had a problem. Well 6 years of tiny splashes and drips and spills rotted away most of the wall. Mold everywhere!!! It was bad!!!

 

[fishforme]

I just started a tank and do not have glass under my two 250W MH... If you have a canopy and you don't push it all the way against the wall, I don't see a problem. Especially, if you manufacture the canopy to eliminate the splashes... Plus, a portion of the light actually gets lost though the glass (about 15%) and without glass, the tank has a better oxygen absorbtion rate due to the airflow... Just my thoughts though...

 

[option720]

I agree with Fishforme-
Keeping glass on the tank will help restrict the oxygen exchange. I use Egg Crate on top of my tank, but i only have PC's so heat is not an issue like it is for you. But i would keep it off.

 

[mr . salty]

Another problem with glass lids is salt build up.You will find yourself cleaning this glass WAY more often than you would like..Plus add the HEAT of the bulb,,,and this salt gets baked on.Then you must SCRUB and SCRAPE it off weekly...I have NO GLASS under my MH's...

 

[garyfla]

Hi
Has any one given any thought to the "incidental" IR and UV produced by
HID lighting? I read an ANSI rating on several bulbs and was surprised at the levels
produced.Even though the bulbs have double
housings They recommended uv shields such
as lexan where the lights are used in close
proximity.There was also great variation from bulb to bulb from the same manufacturer.
Something to think about not only for our own eyes but the sterilizing properties of uv. Gary fla

 

[donm]

OK so I think it will be no glass lid for me. Thanks for all the opinions. Now with no glass lid, what is a safe distance for the bulb to be from the water level?
Also, is it safe to run an atinic bulb through the reflector area of the MH? I was thinking the heat may be a problem. How have you guys worked it out? Sorry about all the questions, but I'm anxious to get started making a canopy.
Thanks,
Murphy

 

[lilmojo79]

You want at least 10 inches if not more from the bottom of the bulb to the surface of the tank. This a minimum, my canopy has around 14 inches, but I think 12 would be ok. What I did with mine was have the Halide 14 inches or so from the water, and have 1x4's extending from the sides inside the canopy to mount PC 50/50 lights to. This way the MH is still a safe distance from the water and the PC's are only about 6 inches from the water so not to lose their intensity. This worked great for me. Also you want to coat the inside with a white or reflective paint/epoxy to help reflect light towards the tank. I bought some silver/chrome paint, painted the inside then used an acrylic sealer to seal the paint in and protect from the salt water.

 

[donm]

Wow! 10 inches above the water is alot. I guess we are dealing with something real and breakable next to water though.
Thanks for the reply, I'm going to give it a try.
Murphy

 

[mr . salty]

I believe that 10" is a little excessive.My two 175watt MH's are only 4" away from the water( or closer).There has NEVER been any problems.The worst that I have had is a little salt residue on the bulbs,but this wipes off easily under running water with a soft towel.AND YES,I have splashed small ammounts of water on them when they were hot,,,And they did NOT EXPLODE.I believe that you would have to totally immerse the HOT bulb into water to blow one up...UNDERSTAND,I am NOT reccomending that you put them this close to the water.But I have,and they DO WORK,They DON"T explode,And they DON'T cook my fish...Just trying to put an end to this MYTH.

 

[lilmojo79]

I am just suggesting the distance from the water to allow for more air to circulate around the bulbs to dissipate the heat. I imagine that you could place them closer, but if at all possible I would put them up higher to lessen the heat under the hood. Just a suggestion, no offense Mr. Salty, I hope I one day become as knowledgable as you about saltwater! And I should if I keep reading and learning from this site!

 

[mr . salty]

Placing them higher above the water will not decrease the heat from the bulbs.They get HOT,and there is nothing you can do about that.But you can disapate this heat by installing a small fan or two to keep fresh air circulating around them.These fans need not be anything fancey either.I got two 3" desk type fans for $5 each and put them at the rear of my hood.They have been running almost 24/7 for about a year now,and make a big diference...

 

[josh]

Option720:
Thanks for the eggcrate idea, I also have PC lights. I often wonder about O2 transfer and it seems that would solve the problem. Have you ever had problems with heat, I have JBJ with two built in fans and the plexiglass cover with water proof caps.
Thanks,
Josh