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Lighting height from a moisture perspective

960 Views 3 Replies 4 Participants Last post by  houstonhobby
Please feel free to chide me for missing an obvious thread (as long as you include a link), but, search as I might, I'm having some trouble finding information on lighting height from a moisture/safety standpoint. I understand the basics of the effect height will have on the PAR, and there are plenty of DIY examples and step-by-steps regarding canopies.

But is there a simple rule of thumb for minimum fixture height above water level, with or without a glass tank cover? I'm on the verge of constructing my own canopy, but I'm having trouble deciding exactly how large to make it, and whether I need to buy or adapt a clear plastic cover for the lighting retrofit. I just don't know how much of a problem moisture (or heat, for that matter) is likely to be. Any links to calculators, articles, or posts, as well as any personal experiences, would be greatly appreciated.

30g Oceanic cube (NOT Bio Cube). Cryptos and Anubias. Current lighting is a woefully underpowered Coralife mini PC with 18W total (not my fault! I inherited!) sitting on a glass lid. Top rim is 20.5 x 18.5 inches. Odd measurements, I know, which is partially why I don't want to buy a premade fixture. Rim is also especially thick, so an (upgraded) Aquaclear 70 doesn't slide all the way on (it works, but the waterfall is about 1/2 inch higher than designed).

Please be gentle - this is my first post, and I'm 2 months into the hobby. Thanks in advance for taking the time to read!

P.S. unrelated question: I also have a 25g with an eclipse 2 hood. I'm contemplating getting rid of the hood, or just cutting it apart, based on whether it will be possible or advisable to switch out the stock ballast with with a 60+w electronic ballast (or two 30+w ballasts?) in order to 2x OD the tubes. Currently holds 2 15w 18" tubes. Not sure of the ballast type atm (two or just one) - it's sandwiched between the fixture and the hood. Current hood has a clear plastic cover for the tubes, with almost no ventilation. Will heat be a problem? And is this even possible?
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I have never seen any information, based on tests, about how much air gap you need to avoid moisture problems. But, it makes sense that if you have the light fixture held above the top of the tank at least an inch or so there would be enough air circulation to avoid any serious condensation problems. On the other hand, I have an 8 gallon nano cube tank with two CFL bulbs mounted in the hood, and no glass or plastic moisture barrier. That hood sits right on top of the tank, putting the bulbs about 1/2 inch above the water. It has been running for about 2 weeks now, and no condensation problems that I can see. I do have an aluminum reflector too, which I grounded.

I'm not even sure how to do a test to find the best or minimum spacing. If you can think of something, please try it and let all of us know what you find out.
Excellent point about glass cover or no glass cover in the light intensity data. I am interested in this question myself.
I used regular "tombstone" t8 fittings over my 120 for many years. This was without a glass top. Was a long time before they showed any degradation. I avoid glass over the tank like the plague, and if the fittings come with a plastic hood I remove that too. I don't want anything between the bulb and the water surface.

If you are buying tank-ready lights I wouldn't worry about it.
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