HELP: Metal Halide Placement ?

[seamist]

I have a 24" tall tank, with a 12" tall canopy. I just bought a 175 watt metal halide hood, its about 6" tall.

Now the problem is the the MH hood would not fit into the canopy, so I just placed the hood on top of the open canopy. This seem to be the only way.

From the MH bulbs to my the top of the water is about 18-20" and another 24" to the bottom of the tank. Corals are place in the middle of the tank.

Would this still work ?

Thanks

Tom

 

[Yinger]

i read that it with a 24 inch tall tank you should have at least a 250 watt bulb. It might be placed a little too high so your loosing some of the par. Maybe lower a little bit?

 

[CMReefer]

a 175 watt MH isn't necessarily too little light for a 24" deep tank, it depends what corals you plan to keep. I agree that you may not be able to keep SPS on the bottom of a 24" tank, but anywhere from halfway to the top should be okay.. As the light travels through air it is restricted very little so having it 20" above the water surface probably doesn't affect the light levels underwater much at all. You definitely could lower it at least 6" without worrying about heat, but I wouldn't worry about lack of light unless you plan to have an SPS only tank.

In short, I think you're okay

Danny

 

[gcarroll]

<a href=showthread.php?s=&postid=7377933#post7377933 target=_blank>Originally posted</a> by CMReefer
I agree that you may not be able to keep SPS on the bottom of a 24" tank, but anywhere from halfway to the top should be okay.. As the light travels through air it is restricted very little so having it 20" above the water surface probably doesn't affect the light levels underwater much at all.

Sorry but I would definitely disagree. Per Sanjay Joshi's reflector research, most reflectors showed a decrease in par when measurements increased from 6ââ"šÂ¬Ã‚ to 12ââ"šÂ¬Ã‚ from the lamp. This loss was normally 30+%. The loss of par at 18+" should be compounded. Now add that to the fact that once the light passes the water's surface PAR levels drop faster than a rock!

Normally it is true that a 175 watt halide is normally sufficient to provide enough light to care for sps down to a maximum of 18". But since mounting it 12" above normal height would yield 50+% less light, I would recommend no sps at all for this tank with the exception of the very lowest light dependent species. I will admit that over the short term you may experience some (pseudo)success but they will most likely become or remain brown while they slowly die.

Seamist, you should try to find a reflector that will fit within your canopy or consider a pendant style reflector that can be used without one. If your tank is a softy of LPS tank you will probably be fine with the exception of the cosmetic look of the whole thing.

 

[Yinger]

<a href=showthread.php?s=&postid=7378439#post7378439 target=_blank>Originally posted</a> by gcarroll
Sorry but I would definitely disagree. Per Sanjay Joshi's reflector research, most reflectors showed a decrease in par when measurements increased from 6ââ"šÂ¬Ã‚ to 12ââ"šÂ¬Ã‚ from the lamp. This loss was normally 30+%. The loss of par at 18+" should be compounded. Now add that to the fact that once the light passes the water's surface PAR levels drop faster than a rock!

Normally it is true that a 175 watt halide is normally sufficient to provide enough light to care for sps down to a maximum of 18". But since mounting it 12" above normal height would yield 50+% less light, I would recommend no sps at all for this tank with the exception of the very lowest light dependent species. I will admit that over the short term you may experience some (pseudo)success but they will most likely become or remain brown while they slowly die.

Seamist, you should try to find a reflector that will fit within your canopy or consider a pendant style reflector that can be used without one. If your tank is a softy of LPS tank you will probably be fine with the exception of the cosmetic look of the whole thing.

that's what i meant to say haha... jk

 

[spline9]

You will also lose par due to dispersion of light. Light is emitted from the pendant in a (relatively) conical manner. You will lose intensity simply because a large portion of the light is being shot out towards the walls.

 

[seamist]

I just gutted the hood. I took out the cords and the ballast for the Metal Halide bulbs.

I bought 3 spider refectors and re-wired each back to it original power cord and connected to the ballast. Now all 3 refectors fit into my canopy perfectly.

Now they are about 8-10" above water line and about 27-30" to the top of the bottom live sand. About 6-10" closer than before.

thank you for all your helps.

 

[gcarroll]

You are set! Happy Reefing!