how high should MH be over water line?

johnvu713 · 02/05/2006, 12:16 AM

i have a 400w single end MH at 13 inches above waterline. should i lower it? how low?

Bebo77 · 02/05/2006, 12:18 AM

you could 8 inches is good so long as its not over glass or acrylic

thereefmaster · 02/05/2006, 01:00 AM

6-8 inches is probably fine, but watch your temps. do you have a chiller at all? if you don't, you might have to invest in one.

HTH

-Nate

Larry Waughon · 02/05/2006, 01:12 AM

I keep them at 8" to 10". I run a fan in my canopy to get rid of some of the heat.

Blown 346 · 02/05/2006, 03:27 AM

I have mine at 12 inches from the waters surface.

ravenr · 02/05/2006, 04:07 AM

Hey Bebo, you say not over glass...why, I have a 6" wide glass support on top of the tank...what gives?

johnvu713 · 02/07/2006, 01:20 AM

maybe i should lower it to a couple more inches. I dont have a chiller but can compensate heat with lot of fans. I'd be needing lot of them as my tank is in the garage

JmLee · 02/07/2006, 02:16 AM

ravenr i wouldnt worry i have two 250 watts mounted 9 inchs above the water line and i have a acrylic tank. Its all jesus no worries. Just watch those temps.

mcox33 · 02/07/2006, 02:31 AM

The glass will magnify the heat coming from the bulbs and put it directly into the tank.

I have my 400 watt MH between 8 and 9 inches above the water surface.

JR719 · 02/07/2006, 02:54 AM

Mine are 9" above and I have to run a chiller. I don't have any fans in the canopy though. I'm sure fans would cut down on some heat.

boxfishpooalot · 02/07/2006, 05:34 AM

Quote:

Originally posted by ravenr
Hey Bebo, you say not over glass...why, I have a 6" wide glass support on top of the tank...what gives?

The glass will magnify the heat coming from the bulbs and put it directly into the tank.

Sorry not true. The truth is if you place a metal halide over a glass support, its going to bust the glass from heat!One drop of water on that glass while hot will cuase the glass to condense sharply and crack your center brace. Any change in heat to the water is bs

Metal halides will heat up the tank at any spot.

Bebo77 · 02/07/2006, 08:14 AM

Quote:

Originally posted by ravenr
Hey Bebo, you say not over glass...why, I have a 6" wide glass support on top of the tank...what gives?

yeah it can warp acrylic if you leave it over it.

And it can stress the glass. You want to keep halides off of bracing on top of your tank.

02/05/2006, 12:16 AM	#1
johnvu713 Moved On Join Date: Sep 2005 Location: houston Posts: 732	how high should MH be over water line? i have a 400w single end MH at 13 inches above waterline. should i lower it? how low?

02/05/2006, 12:18 AM	#2
Bebo77 Premium Nonpaying Member Join Date: Jul 2005 Location: Lost Posts: 14,377	you could 8 inches is good so long as its not over glass or acrylic __________________ Gabriel Current Tank Info: 300 Gal Envision Tank(98Lx30Wx26T) 120 Gal SoCalCreations Sump, Deltec TC2560, 2 LumenarcsMini 1 Reg on a light mover W Radiums 250& 400, Gallaxy ballasts, Red Dragon 10m3 return W/ 2 WavySeas, 2 6155 Tunze streams

02/05/2006, 01:00 AM	#3
thereefmaster Registered Member Join Date: Jun 2005 Location: Mossyrock, WA Posts: 354	6-8 inches is probably fine, but watch your temps. do you have a chiller at all? if you don't, you might have to invest in one. HTH -Nate __________________ Click on the Little Red House to see my Reef! Current Tank Info: 55G Reef, Coralife SuperSkimmer 220, Current USA 260W PC, 2" SSB

02/07/2006, 02:31 AM	#9
mcox33 Registered Member Join Date: Mar 2004 Location: Nitro, West Virginia Posts: 2,261	The glass will magnify the heat coming from the bulbs and put it directly into the tank. I have my 400 watt MH between 8 and 9 inches above the water surface. __________________ Mary Current Tank Info: 90 Saltwater Reef, 2 x 400 watt MH, 4 x 65 watt PC, 1 x 24 watt 48" T-5 + 4 blue led's, Dual chamber MRC Calcium Reactor, Huge DIY Kalkwasser reactor (made by someone else) Auto Top Off and Aquatecture Plus Skimmer

02/07/2006, 02:54 AM	#10
JR719 Tang Cop Join Date: Sep 2004 Location: OK Posts: 2,240	Mine are 9" above and I have to run a chiller. I don't have any fans in the canopy though. I'm sure fans would cut down on some heat. __________________ Can't sleep, clowns will eat me. America is the most grandiose experiment the world has seen, but, I am afraid, it is not going to be a success. Sigmund Freud Current Tank Info: 300 reef, Aqua controller, Deltec calcium reactor, Reeflo 250 skimmer, Icecap bla bla bla

02/05/2006, 01:12 AM	#4
Larry Waughon Registered Member Join Date: Apr 2004 Location: Pingree Grove, IL Posts: 1,872	I keep them at 8" to 10". I run a fan in my canopy to get rid of some of the heat.

02/05/2006, 03:27 AM	#5
Blown 346 Registered Member Join Date: Apr 2004 Location: Rockford, Illinois Posts: 6,596	I have mine at 12 inches from the waters surface.

02/05/2006, 04:07 AM	#6
ravenr Registered Member Join Date: Nov 2005 Location: Long Island, NY Posts: 64	Hey Bebo, you say not over glass...why, I have a 6" wide glass support on top of the tank...what gives?

02/07/2006, 01:20 AM	#7
johnvu713 Moved On Join Date: Sep 2005 Location: houston Posts: 732	maybe i should lower it to a couple more inches. I dont have a chiller but can compensate heat with lot of fans. I'd be needing lot of them as my tank is in the garage

02/07/2006, 02:16 AM	#8
JmLee Registered Member Join Date: Jan 2006 Location: Hohensfels, Germany Posts: 1,545	ravenr i wouldnt worry i have two 250 watts mounted 9 inchs above the water line and i have a acrylic tank. Its all jesus no worries. Just watch those temps.