MH lamps melting tank

[Jon91zX]

Ok I have had these 250 W x 2 10k ushio metal halides running for a couple of hours and i beleive they are causing the top of my acrylic tank to warp. It is 1/2 inch polycast acrylic and the lamps are about 4" off the top of the tank and 6" or so off the water.

Should i remove the tops of my tank? if i do that the water splashes on the bulbs and gets salt all over them... im not sure what to do any suggestions? Is it even possible for the acrylic to melt or is this just my imagination?

Tank:
120G 4'x2'x2' 1/2" acrylic
Lights:
2x250 W MH retrofit, 2x 110 W VHO, 2 x 4" fan cooling kits

 

[Christeon]

I was asked about it with my last Lighting question, I have glass so it's no problem. But yeah you can melt plastic with heat anyday.

 

[CG1]

Ok I have had these 250 W x 2 10k ushio metal halides running for a couple of hours and i beleive they are causing the top of my acrylic tank to warp. It is 1/2 inch polycast acrylic and the lamps are about 4" off the top of the tank and 6" or so off the water.

Should i remove the tops of my tank? if i do that the water splashes on the bulbs and gets salt all over them... im not sure what to do any suggestions? Is it even possible for the acrylic to melt or is this just my imagination?

Tank:
120G 4'x2'x2' 1/2" acrylic
Lights:
2x250 W MH retrofit, 2x 110 W VHO, 2 x 4" fan cooling kits

Four inches is simply too close - please do not remove the lids, splashing water will occur and a mess will shortly follow. You need to move those lights up two to four additional inches and you will be fine.

 

[mgranato]

Agreed, 4 inches is dangerously close! Back those puppies off. I have the same lights and acrylic and keep mine 10" away and still get enough light to reach my SPS in the bottom 1/3 of the tank. Make sure you don't have any bulbs directly over your structural struts, no matter high high they are from the acrylic, that's a true recipe for disaster.

 

[mgranato]

One other thing, you may want to get glass tops (1/4") instead of acrylic. I believe the 1/2 acrylic will block way more useful light than thinner glass, and acrylic will always want to warp towards a heat source. Either way, raise those lights.

 

[IceMan0124]

yeah, 8-10" from the top of the tank is the bare minimum distance IMO, having the bulbs as close as you have will probably lead to some fairly heavy heat issues as well, you might want to forgo the tank tops alltogether, and just run some mesh around the inside lip a few inches out for jumpers, and use a shield over the bulbs themselves

 

[stubbsz]

Mine are 7 inches above the acrylic *. It still feels warm. I also made the point of centering my mini-pendants above the large access wholes in the top so that I lose as little of the light as possible and directly heat the acrylic as little as possible. I chose my lighting configuration to help as much as possible.

-Adrian

*I love "working from home" on Thursdays, I could actually go measure that to make sure

 

[ChrisRD]

I agree with the idea of raising the lights as everyone has mentioned. Personally, however, I never run a halide lit tank with acrylic or glass covers. IME having the tank this tightly covered leads to overheating in the Summer months and can also create pH issues (lack of gas exchange).

 

[stubbsz]

Are we talking about a tightly covered tank here though or one with the usual wide skirt of acrylic around the edges with big holes in the top. I don't have many heat issues in CA with no chiller and one fan blowing on the water surface. 500 Watts of HQI
-Adrian

 

[Jon91zX]

ok well i solved my bubble issue and removed the covers. now it is much cooler in the canopy and dont believe i really have an issue nemore. I wish i could raise the lights but as of now i cant do nething about it. In the future i will try to raise them but now the tank is uncovered so yes it is the acrylic with wide skirts and large open L shaped holes. looking great btw im posting some pics in the tank specifications section in a bit so u all should check it out!