retrofits for canopy

[lorin]

I am starting a 29 gal reef tank. There is a canopy over the tank. I found a 2-foot retrofit with 1 MH 175 watts and 2 PC compacts 55 watts that will fit. 1) Can I screw the retrofits to the top of the wood canopy. What are retrofits? 2) This lighting system offers a lens that will shield the lights from moisture. I will only have a few extra inches between the lights and water. Will the lights overheat my tank and will I need a special lens to block AV light?

 

[tracklighter]

I was all set to buy a MH set up for my 29 gallon, but I found out that with my canopy the light will be too close to the water. I have heard from people on this board not to set the MH too low to the water line. A rule of thumb I have seen most often: Set the MH so that it is at least 8 inches from the water. You run the risk of water splash if it is lower. This could lead to bulb damage or even fire. Also, the lower the bulb the more it will heat the water.
A retrofit is a kit that you place in a pre-existing canopy. You can screw retrofits to the top of the wood canopy. Be careful about the heat transfer from the MH kit to the canopy. Fans can help blow off some of this heat.
There is a lot of advice given on this board about setting up MH systems. Try doing a search.
When I look at some of the tanks with MH (particularly the 20k radiums) I am very tempted to get that set up. But my canopy is just too low for it.
I really don't understand the concept of UV lens protection and why it is needed at all. Do the mh bulbs put out more uv light than natural sunlight? If not then why is a uv lens needed? Maybe someone else can explain this.

 

[cap'n pete]

Definately don't install a MH less than 6 inches from water. Most recommend at least 10 inches of clearance. That would be a great light for a 29G, but your going to have to get a new canopy. Some MH bulbs produce UV rays at a much higher rate than natural sunlight. The individual bulb manufacturer should be able to tell you what bulbs need to be behind UV blocking glass. HQI bulbs are well known for UV. See if the company that sells the retro knows, if not contact the manufacturer directly. Fans are also recommended to disperse the heat of MH bulbs. These bulbs are very intense and very hot, placing them too close to water and not allowing adequate ventilation will cause extreme temperature rise in the tank if not worse.

 

[lorin]

Thanks for your help. I will try different options. I do not have the canopy, I am planning to buy one this week. I like the MH lighting, that is my first priority. Then I will work on the canopy.