lighting question

[is_that_a_fish]

my little bro is really getting into the reefing hobby, he purchased a 28 gallon bowfront about a year ago and it is coming along nicely. Anyway he has pc lights on it currently, but has decided to switch to 400w of metal halide (which he has already bought) big change i know. Anyway the 400w metal halide is in a pendant and his tank is only about 2 feet long with a center brace, so the question is, if the pendent was centered over his tank, will the tank still get adequate light to keep the likes of sps and anything else he wants in there? or will the brace just cut out to much light? would it be a better idea to have the light off centered so that one side gets an extremely crazy amount of light and the other side gets a little bit? Any advice is appreciated. thanks in advance.

 

[mufret]

The center brace will certain cause a shadow however, if it a plastic center brace, the bigger concern would be the heat generated by a 400w MH. There's a chance it might melt the center brace!

 

[is_that_a_fish]

yeah, i thought about the melting thing as well, but since its a 400w metal halide, and has a pretty good amount of penetrating power, i was thinking of maybe placing a little bit higher and having a fan blow sort of around the brace, so it doesnt get to hot. Im just worried whether or not the brace will cut off a good amount of light.

 

[ouling]

It will not melt at all, trust me, I have two 400w over my tank at 7'' without any protective glass.

It takes over 300degrees f to melt those kind of plastic

 

[xyzpdq0121]

Mike, Does a 28 gal bow front need a center brace?!?

 

[wbholwell]

I've heard that the bowfront designs are less structurally sound at the seams. And it's actually the depth of the tank that determines the pressure exerted- how tall is the 28 gal bow?

 

[mufret]

ouling;58543 wrote: It will not melt at all, trust me, I have two 400w over my tank at 7'' without any protective glass.

It takes over 300degrees f to melt those kind of plastic

Are any of your bulbs centered and directly over the brace in your tank? You'd be surprised at the amount of heat that's generated by a 400w bulb. I've seen quite a few "melted" center braces in my time in this hobby that were caused by placing the lighting too close to them.

Raising the fixture will help the heat issue but it will not get rid of the shadow the center brace will cast. As far as whether one is needed, that would not be something I'd be comfortable giving an opinion on. The manufacturer felt like they needed one.

Is the fixture already over the tank? What's the temp of the tank?

 

[simon_kruger]

Mike,

I agree, I've melted a brace before and the 400Watt was about 8 inches away.

 

[is_that_a_fish]

right now, the fixture is about 8 inches above the tank, and there is a fan blowing under it (kind of directed towards the brace, but it still blows on the tank as well), the temp im getting seems to be a steady 80 degrees right now.

 

[daveatl]

You can cut a majority of the plastic center brace and replace it with a SS wire, I've seen it done several times.

I'm guessing that the 28 is one of those self-contained units (no sump), I think that a 400w MH is going to bake that tank, both in terms of too much light and in heat generated.

 

[ouling]

My fault. I didnt know your tank was a small one and with a centerbrace dead in the middle of the light. But if they say it would melt then I would take some precautions, but the light does not generate that awesome amount of heat to melt the plastic when it's higher up-in most peoples opinion. I have an acrylic canopy that is used to cover the tank at night so bugs don't get in, due to my LEDs, and I always forget to take that piece off when I wake up, the acrylic canopy never melted despite being only 6.5'' away from the 400w 10k bulb that is ran by the most powerful ballast available. Acrylic melting point is in the neighborhood of 200-300 and hard plastic is 300+. If it's 400w, 8'' off the brace, you will be fine 100%.