View Full Version : MH users - PAR question

06/27/2017, 07:59 AM
Hi ,

I currently run 2x250 watts radiums on magnetic ballasts over a 30 in x30 in x18 in tank . I have been toying around with the height of the fixtures over the tank and currently set at 9 inch from the tank .
Mainly ranging from 250-400 across the tank .
I want to know what you guys run the PAR at and what height do you have your halides set at .
I can definitely bring it lower if need be but want to know your suggestion .

Oh tank is all acro. Alk running at 8.2-8.5


06/27/2017, 08:19 AM
On a tank that size you should only need 1 radium. What type of reflector do you use? When I ran radiums anything closer than 12" cooked my tank and increased evaporation too much. If you raise the lights up to 12-14" I bet you could get away with just 1 radium provided you have a good reflector.

06/27/2017, 08:29 AM
Currently using old lumemarc minis . I went with 2 reflectors as it's a30 in x30 in square which was difficult to be covered with one reflector as my layout is pretty scattered all over .
Aim is to grow acros anywhere ..

Yes, evaporation is a lot but I live in a cold climate and have the ability to run 3 fans over my sump to keep the temperature below 78 f


Big E
06/28/2017, 02:47 AM
I agree with the above suggestion, you should only need one bulb and a larger reflector Most are in the 19-20" size and will cover 30x30.

Any of the large reflectors will work well. You could also look in the used section and find Lumenarc 3 or other similar brands for sale.


I know this isn't what you're asking but this will save on elect. bulbs, & less heat.............you should still have plenty of par for the acros.

06/28/2017, 06:12 AM
Thanks Ed for the reply . Well my aquascape is like pretty flat except for a little high rise of the left side . Hence thought of using 2 metal halides in small reflectors over each island area .
Definitely will start looking into the larger reflector options but need square ones as I run reefbrite tech leds for 11 hours with halides running for 5 hours .


06/28/2017, 06:21 AM
For SPS, I keep 800 (shadows) to 1600 (highest lit) on the water surface.

Here's a surface PAR map showing new bulbs (top) and old bulbs (below)

<a href="http://s1062.photobucket.com/user/karimwassef/media/LED%20experiments/Capture_zpsqflx1soi.png.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/LED%20experiments/Capture_zpsqflx1soi.png" border="0" alt=" photo Capture_zpsqflx1soi.png"/></a>

I've since replaced the reflectors on the side to the same as the middle.

<a href="http://s1062.photobucket.com/user/karimwassef/media/4A261F16-3008-4CFA-B046-391D6D9C3977_zps6ftrjkvz.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/4A261F16-3008-4CFA-B046-391D6D9C3977_zps6ftrjkvz.jpg" border="0" alt=" photo 4A261F16-3008-4CFA-B046-391D6D9C3977_zps6ftrjkvz.jpg"/></a>

06/28/2017, 07:07 AM
What reflectors are you running now ^^^. Im getting ready to upgrade mine. Thanks

06/28/2017, 07:59 AM
I use Hamilton Cayman Sun 400W about 12in over the water

06/28/2017, 08:09 AM
karimwassef, what program did you make that PAR chat in? It's awesome.

06/28/2017, 08:28 AM

Collecting the data took the longest time


06/28/2017, 09:36 AM
Nice work. I gotta say, I'm always impressed by your DIY skills and ambition.

06/28/2017, 09:51 AM
I keep mine 4-5" over the water... just enough to get some air flowing through there. I have 600 at the top of the rocks (4-5" under) and 250 in the sand. This is 14K Phoenix on M80. Radiums on M80 are nearly the same for me. I have a 250W Radium on M80 in a Cozumel Sun (large) reflector and it is about 750 in the frag tank a few inches under the water.

06/28/2017, 11:22 AM
I take a surface water map since depth PAR is just a function of placement, shadowing and clarity. If I get the right surface map, I know the rest without having to do a 3D.

I did envision using a printer-like robotic fixture that would sample the entire volume instead of the surface, but that was just too much effort.

I will say that spot-measurements of PAR are not very useful to me. Until I ran a full map, I couldn't understand why some of my sps were growing sideways under "what appears to be" the same light. But seeing the gradient in PAR over a couple of inches made it very clear.

06/28/2017, 11:27 AM
I do this with LEDs too, by the way. Here's my DIY 500W LED "wall" PAR map
<a href="http://s1062.photobucket.com/user/karimwassef/media/LED%20experiments/0_zpsg70aruxp.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/LED%20experiments/0_zpsg70aruxp.jpg" border="0" alt=" photo 0_zpsg70aruxp.jpg"></a>

It's 500W over a large surface area ~ 2' x 4' so the PAR is lower but it is more uniform.

06/28/2017, 03:56 PM
Thanks guys for all your replies .

@jda - well I do get similar par with lowering of my reflectors but fear that might get too much light for my acros and cause bleaching . Are you happy growing acros on the sandbed with 250 PAR ?

@karim - amazing info and Diy skills . So if I understand correctly ,it makes more sense to measure PAR at the top of the water surface than below it ?


06/28/2017, 04:02 PM
It's about a standard approach (I'm an engineer). If I'm comparing lighting options, I need to establish a common standard for measurement and I choose the top surface since I know the loss in PAR vs. distance formula. I can basically predict PAR anywhere if I have that surface PAR map.

Someone else may choose to measure PAR on the sand floor instead. That's much harder.

My convention is at the surface (actually 1" above the surface to be exact). If you want to compare results to mine, then the same measurement standard becomes an objective comparison point.

06/28/2017, 05:51 PM
@jda - well I do get similar par with lowering of my reflectors but fear that might get too much light for my acros and cause bleaching . Are you happy growing acros on the sandbed with 250 PAR ?

I see no harm is getting corals as much light as possible. The only real exceptions to this are some deepwater acros, which I do like the color (deeper) of under 300 PAR, but they don't grow as well.

This applies to softies too. I farm bounce and jawbreaker mushrooms under a Radium in 3" of water in my frag tank - you can buy a lot of nice acros with babies of these. They grow pretty fast - nickel to half dollar in a few months under Radiums in clean SPS water.

07/09/2017, 01:47 PM
I got an awesome deal on a Hamilton comuzel reflector with ballast which is 20 in x20 in x9.5 inch . Wondering if it would be enough for my 30 in x 30 in x18 in acro tank ?
Now I can even run a 400 if it's better suited ..


07/09/2017, 02:40 PM
I've got a 400 watt Cayman Sun, which has a 13x13 reflector, over my 36x36x27 tank. I don't know the PAR, but it visually covers the tank quite nicely.