How high above tank for T5/MH fixture?

Aquavaj · 06/21/2018, 12:00 PM

Tank is 36L x 15H. Fixture is 36" with 4x39w and 250w MH DE @ 14k. I currently have it hanging 12ft above the tank. Tank is still cycling so no livestock yet. Will be going LPS and softies first so will be using just the T5s. Once the tank is more established I'll add some sps and let the MH kick on for midday.

Would 12ft be too low for only a 15" high tank? I think any higher and the T5s lose a lot of intensity but with the MH on and it might be too much.

mcgyvr · 06/21/2018, 12:03 PM

huh? 12ft?
Did you mean 12 "inches"

My t5s are like 10 inches off the top of the water in a 16inch deep tank..
When I ran MH bulbs I think I had mine like 18 inches of so off the water..
12feet is way too high..

sfdan · 06/21/2018, 12:22 PM

There is really no right answer to this question.

By lowering the bulbs you:

1. Get more PAR in the tank
2. Add more heat to the tank
3. Concentrate the light more (though this depends heavily on the type of reflectors)

By raising the bulbs you do the opposite: less par, less heat and the light is more spread out

If you don't have a PAR meter, I'd say you should put the bulbs as low as possible where it doesn't heat the tank up too much and the spread looks good to your eye. That might be 6", it might be 8", it might be 12".

Then just pay attention to the corals and move them around to find good spots for them. The SPS should generally be in the brighter spots and the other corals in the lower light spots.

Aquavaj · 06/21/2018, 03:18 PM

Quote:

Originally Posted by mcgyvr

huh? 12ft?
Did you mean 12 "inches"

My t5s are like 10 inches off the top of the water in a 16inch deep tank..
When I ran MH bulbs I think I had mine like 18 inches of so off the water..
12feet is way too high..

Sorry, yes 12 inches.

Aquavaj · 06/21/2018, 03:57 PM

Quote:

Originally Posted by sfdan

There is really no right answer to this question.

By lowering the bulbs you:

1. Get more PAR in the tank
2. Add more heat to the tank
3. Concentrate the light more (though this depends heavily on the type of reflectors)

By raising the bulbs you do the opposite: less par, less heat and the light is more spread out

If you don't have a PAR meter, I'd say you should put the bulbs as low as possible where it doesn't heat the tank up too much and the spread looks good to your eye. That might be 6", it might be 8", it might be 12".

Then just pay attention to the corals and move them around to find good spots for them. The SPS should generally be in the brighter spots and the other corals in the lower light spots.

Yea I guess I'll know better once I get some corals in there. But at it's current height the light spread looks good to my eyes. The heat is minimal but a few more inches should make it a nonissue.

sfdan · 06/21/2018, 04:46 PM

Quote:

Originally Posted by Aquavaj

Yea I guess I'll know better once I get some corals in there. But at it's current height the light spread looks good to my eyes. The heat is minimal but a few more inches should make it a nonissue.

Some heat is certainly fine. My tank heats up about 3 degrees from the start of the day to the end of the day based on the lights and my corals have no ill effects. That is about the most temperature swing I'm comfortable with but I've read other people have even higher swings.

Of course there are lots of other ways to lower the temperature of your tank without raising your lights if you really want to get the intensity as high as possible. Though for your needs it doesn't sound like you are chasing the ultra high intensity.

But it really is all about the coral health. If the softies/LPS are doing well and your SPS are keeping their color, you know the lights are fine. If the SPS are browning out then maybe you'll need to lower the lights a little bit.

biecacka · 06/28/2018, 07:07 AM

I run my dual 250 halides about 7 inches off the water.

Corey

Holyreefer · 12/14/2018, 08:13 PM

Quote:

Originally Posted by biecacka

I run my dual 250 halides about 7 inches off the water.

Corey

Glad to hear I’m not the only one using MH

Syntax1325 · 12/15/2018, 07:18 AM

On a 180 I run my lights about a foot above the top frame of the tank. A foot above a shallow tank seems unnecessary maybe?
I guess it depends on how much par you are looking to give your corals.

There are many of us who use mh.

Sent from my iPhone using Tapatalk

Seasidenj · 12/20/2018, 09:33 PM

12 to 16 inches would be about what you would need

candymancan · 12/21/2018, 12:00 AM

I dont have metal halides but i do have a 4x24w T5 fixture above my 60g hexagon. I have the lights maybe 8 inches above the tank ?

06/21/2018, 12:00 PM	#1
Aquavaj Registered Member Join Date: Jun 2014 Posts: 132	How high above tank for T5/MH fixture? Tank is 36L x 15H. Fixture is 36" with 4x39w and 250w MH DE @ 14k. I currently have it hanging 12ft above the tank. Tank is still cycling so no livestock yet. Will be going LPS and softies first so will be using just the T5s. Once the tank is more established I'll add some sps and let the MH kick on for midday. Would 12ft be too low for only a 15" high tank? I think any higher and the T5s lose a lot of intensity but with the MH on and it might be too much.

06/21/2018, 12:03 PM	#2
mcgyvr Registered Member Join Date: Sep 2003 Location: North Carolina Posts: 20,050	huh? 12ft? Did you mean 12 "inches" My t5s are like 10 inches off the top of the water in a 16inch deep tank.. When I ran MH bulbs I think I had mine like 18 inches of so off the water.. 12feet is way too high.. __________________ Who me?

12/15/2018, 07:18 AM	#9
Syntax1325 Acro Addict Join Date: Jan 2003 Location: Maine Posts: 598	How high above tank for T5/MH fixture? On a 180 I run my lights about a foot above the top frame of the tank. A foot above a shallow tank seems unnecessary maybe? I guess it depends on how much par you are looking to give your corals. There are many of us who use mh. Sent from my iPhone using Tapatalk __________________ Back to halides and loving it! Current Tank Info: 180g sps dom, 40b sump, Reeflo Dart, Apex, Aquamaxx co2, Reefbrite mh/led pendants w/14k twinarcs, Kore 5th doser, Tunze ATO, Ranco controlling 800 watt Finnex tube, 2 Maxpect Gyre 150XF with Ice Cap Controllers and battery backup, Bean Animal drain

06/21/2018, 12:22 PM	#3
sfdan Registered Member Join Date: Nov 2015 Location: San Francisco Posts: 451	There is really no right answer to this question. By lowering the bulbs you: 1. Get more PAR in the tank 2. Add more heat to the tank 3. Concentrate the light more (though this depends heavily on the type of reflectors) By raising the bulbs you do the opposite: less par, less heat and the light is more spread out If you don't have a PAR meter, I'd say you should put the bulbs as low as possible where it doesn't heat the tank up too much and the spread looks good to your eye. That might be 6", it might be 8", it might be 12". Then just pay attention to the corals and move them around to find good spots for them. The SPS should generally be in the brighter spots and the other corals in the lower light spots.

06/28/2018, 07:07 AM	#7
biecacka Registered Member Join Date: May 2008 Location: Columbus Ohio Posts: 6,361	I run my dual 250 halides about 7 inches off the water. Corey

12/20/2018, 09:33 PM	#10
Seasidenj Registered Member Join Date: Mar 2017 Posts: 55	12 to 16 inches would be about what you would need

12/21/2018, 12:00 AM	#11
candymancan Registered Member. Join Date: Aug 2013 Posts: 124	I dont have metal halides but i do have a 4x24w T5 fixture above my 60g hexagon. I have the lights maybe 8 inches above the tank ?