To cover or not to cover...

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dansemacabre

Aquarium Advice Freak
Joined
Jul 20, 2003
Messages
440
Location
Detroit MI
So, should I place a cover over the water on my 125gallon? hellolights.com says I NEED a glass cover between the bulb and the water. I've read all over here not to do it. My LFS has their halides over open water, albeit roughly 8inches above. So, I'm going to assume hellolights is covering its legal behind, and that it is safe to put the halides 8" above the open water? Should my VHOs be closer? At the LFS, they are the same distance. I think I'm going with 3x250w MH+2x165VHO. Also, which is better as far as magnetic ballasts...probe start or pulse start? thanks!
 
So, I'm going to assume hellolights is covering its legal behind, and that it is safe to put the halides 8" above the open water? Should my VHOs be closer?

It is not "safe" strictly speaking. I run my halide about 6-8" from the water surface uncovered. I haven't had a problem, but one small splash that makes it to the bulb and it will blow. My PCs are the same distance from the water as the halide.
 
My PC's are between 6-8" above the water surface with only air between them. I really dont have an issue with water splashing up onto them. A thin bit of acrylic can be put just below the bulbs if you want. Make sure you use a fan to vent the bulbs if you do this.
 
fishfreek said:
A thin bit of acrylic can be put just below the bulbs if you want. Make sure you use a fan to vent the bulbs if you do this.

Just be sure, as fishfreek mentioned, that you put the cover right below the bulbs. You don't want to use one of the glass covers on the tank. It will trap heat and inhibit gas exchange. The top of the tank needs to be open. None of my lights have covers and I've never had a problem either. You may get a little salt buildup on the bulbs in time, but this is easily cleaned off with vinegar.
 
The only exception to the above great advice would be if you used an HQI system. Those MUST have a glass cover.
 
You need a glass cover over the bulb if youre using a DE halide because there's no uv coating on the bulb itself like a SE or mogul. I wouldnt leave a mh out in the air above water anyway for the reason that reefrunner said.
 
I run PCs, but have the glass tops. What I did was removed the plastic strip on the back side of the glass tops for a vent and placed the lights above the remaining glass portion, plus my sump is uncovered now. Seems to work for me.

I'm a chicken, but I know the whole electricity and water relationship well, I deal with it often.
 
I have PC's over glass. I do that for the safty and also to avoid a corrosion problem. It can be very costly to have to replace a lighting system. I do all I can to preserve the lfe of them.

Howard
 
I'll be using SE 250w bulbs. Ok, so, about how far should the acrylic be from the MH bulbs...so that it does not melt. (What is the melting point for acrylic anyways?) Thanks all, and Happy Holidays!
 
Thanks for the info page, Bearfan. Do you (or others) have a suggesstion on how far from a 250w MH bulb the acrylic should be? I'm not quite sure how hot the bulbs get (I know it's extreme) and while I'm sure I could find it, I'm not sure about how much x heat decreases over n length. I could probably find that too...so I'll go looking, but if anyone already knows about how far, please respond. Thanks everyone! I think I'm on my way to a great tank, and I owe it all to you.
 
Ok, so I found out the surface temp of a MH bulb at that wattage is +475°F. I thought of something (stupid me for forgetting it earleir). I'm going to have some gobies, which I've been told are notorious jumpers. So, I'm thinking I need an acrylic sheet to cover my tank. Here's perhaps the plus side. I'm going to have a refugium, operating at approx 900gph. Will the agitation caused by an overflow box, the trip down the tubes, the skimming, the waterfalls, etc in the 'fuge be enough water exposure to make up for having to cover most of the display tank? Thanks again!
 
I think we need some clarity here. First, you need something to protect the bulb if youre going halide. With a SE youll need a glass or acrylic cover. I doubt it will get anywhere near the melting point of acrylic. You dont want a cover over the tank itself, youll inhibit gas exchange and youll diffuse the light when evaporation occurs. Id use eggcrate over the top if you feel you wana cover the tank or just use tempered glass in the pendant if youre using one.
 
OK. For all intents and purposes, the canopy will be made out of wood, and in a style like you would hang from a ceiling. So let's just say it hangs from the ceiling (whether it will or not, I've yet to decide, but the design will remain the same). I'm supposing it will resemble a box, with vents, with lights in it. The canopy will be made with what I'm guessing will be a nice oak plywood (if this will not work, or is not recommended, please let me know!) The 72" build-your-own MH/VHO retrofit from hellolights.com will be mounted into the top panel of the hood. It will have wood on the sides to hide the actual bulbs themselves from viewing. It will be equipped with some fans to keep down temperature. How far from the MH bulbs should I mount the acrylic? 3", 4", more? less? I like the idea about eggcrate to cover the tank. Thanks for that idea! My only concern is keeping down temp, protecting my bulbs and livestock, and creating the prime lighting conditions for them. So, while I'm at that subject as well, should I go 10,000K on the 2x250 MHs and then 03 actinic on the VHOs? Will this support all the corals+clams, or will I need something different. Sorry for the volley of questions, I just want to do this right. Thanks again!
(P.S. - If I left out any other important info, I apologize. I'm still very new to the saltwater aquarium lighting scene, and well, the saltwater scene in general. So if I left anything out, just remind me/ask me.)
 
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