Question about venting a MH T5 comobo light fixture

[zear0]

I am wondering how critical it is to vent the actual fixture.

If the fixture is suspended above the tank, its easy enough to have a fan blow across the surface of the water to increase evaporation and reduce the heat added by the lights.

In looking at different fixtures, the one's that come with internal fans usually claim that the venting increases the lifetime of the bulbs. Does it increase the lifetime of the bulb's effectice PAR rating? Or is it the overall lifetime of the bulb. My understanding is that bulbs are usually replaced each year, long before they would actually "blow out."

I am considering the following fixture:

http://www.marinedepot.com/md_viewI...dproduct=AQ1831

It has no fans but is kinda cheap.

Is it a bad idea to consider a manufactured fixture housing 2 250Watt MH (with a remote ballast) and 2 54Watt T5 and no cooling fans?

thanks in advance for your thougts!

-Jeff

 

[Anonymous]

Cooling flourescent bulbs will keep the phosphors active longer and thereby increases useful bulb life in terms of PAR. The same is not true for MH bulbs. Cooling MH bulbs won't affect the lifespan. Theoretically, a cooler MH bulb is less efficient but I doubt a small fan can lower the bulb temp of a MH significantly.

The heat from a MH bulb in close proximity to a flourescent bulb can dramatically decrease the lifespan of the flourescent so it is advisable to cool the flourescent bulb.