My par sensor must be wrong

[Webmanny]

Hey guys,

I just finished building my DIY t5/LED hybrid light and decided to test it without any water, but the numbers look very weird.

The light has two 48w LED pucks and two 39w T5 bulbs. It looks brighter than all other lights I have built. However, the par sensor reads 300 at the surface/about 6" from the light and drops to 50 at the bottom/about 23" from the light.

I would love to test it on someone's tank that is close by and knows their light is good. If anyone wants to let me measure their light's par to confirm my meter is correct, I would appreciate it.

Also, could it be that I don't have any water? I would think that it would be the opposite, but I may be wrong.

I live close to Busch Gardens. If you are close by and are willing to let me test this sensor, please send me a PM and we'll coordinate.

 

[rogergolf66]

What makes u think those numbers r bad? What did u plan to keep in the tank? SPS will do well over 250-150 and mix will do well in that 75-150 range Zoas will do well around 50

 

[rogergolf66]

Also remember u have to bump the blue led by 10%-20%

 

[CrazyEyes]

Water really doesn't affect PAR unless it's really dirty or alot of surface movement. 23" from the light is still some distance. Not to mention not using any sort of optics is going to hinder the PAR output. Unless you are looking to keep SPS literally anywhere in the tank I wouldn't worry about it too much. I personally don't think PAR is as important as once thought.

 

[rogergolf66]

Water really doesn't affect PAR unless it's really dirty or alot of surface movement. 23" from the light is still some distance. Not to mention not using any sort of optics is going to hinder the PAR output. Unless you are looking to keep SPS literally anywhere in the tank I wouldn't worry about it too much.

Agreed those numbers will grow coral just fine if the spectrum is correct.

 

[Webmanny]

OK. I feel much better. I was reading about par requirements for some easy sps corals and it said something like 600 par and that freaked me out a bit.

I'm not planning on keeping any sps for the time being, but wanted to have the option if I wanted to.

Thank you all for your response. Have a great night.

 

[MrHarvard]

Your numbers are good enough to grow anything you decide to put in your tank. Your not going to get accurate readings for leds with a regular par meter especially if there in the blue spectrum. There's "supposedly" a formula that you can use to get closer to an accurate reading but I still don't believe it's even close to accurate. Get a reading for only the LEDs with the T5s turned off and see just how low it reads. Par meters are just not meant to be accurate for full spectrum LEDs so don't stress the readings. When I first set up my tank I was running one AI Prime and the highest reading I could get with all channels up to 100% at the top of the tank was around 100 and where I had my SPS placed was only reading 40 on an apogee par meter and they were doing just fine. I have since added a second Prime and the readings were still low yet all my acros are thriving. If your getting a reading of 300 your good to go. Lux meter is much more accurate if you really want to know but I wouldn't even bother. If you don't believe me crank the fixture up and place a frag right up top to start with and see if it thinks you need 300 more par...lol..

 

[Webmanny]

Very good points. I did the same test last night with only the LEDs on, no T5s and I get the same results, which I imagined would be the case, since the LEDs are pretty strong and the T5s are only to supplement the spectrum.

I appreciate you sharing your personal experience and PAR readings. I was freaking out since I was expecting to get much higher readings.

On a side note, I also tested my current light, which is installed on my 36" bow front and growing almost every coral, including SPS and it came back about 20% lower across the board. Please note that I am growing Hammers and Frogspawns like crazy even on the sand bed with this light so... PAR readings with LEDs means nothing I guess.

Thanks again folks.

Your numbers are good enough to grow anything you decide to put in your tank. Your not going to get accurate readings for leds with a regular par meter especially if there in the blue spectrum. There's "supposedly" a formula that you can use to get closer to an accurate reading but I still don't believe it's even close to accurate. Get a reading for only the LEDs with the T5s turned off and see just how low it reads. Par meters are just not meant to be accurate for full spectrum LEDs so don't stress the readings. When I first set up my tank I was running one AI Prime and the highest reading I could get with all channels up to 100% at the top of the tank was around 100 and where I had my SPS placed was only reading 40 on an apogee par meter and they were doing just fine. I have since added a second Prime and the readings were still low yet all my acros are thriving. If your getting a reading of 300 your good to go. Lux meter is much more accurate if you really want to know but I wouldn't even bother. If you don't believe me crank the fixture up and place a frag right up top to start with and see if it thinks you need 300 more par...lol..

 

[Safir]

Fwiw, Mr postal measured my tank with the club's meter and u,see 78 3w less he masured ~100 near the surface and everything we have, sps, lps, softies all grow great for us. My frag tank looks just a sbrigh (again, hardly scientific) and measured in the 300-500 range. In than tank I ha e so.e palys that are in an area that measured well above where the display tank measured and are reaching for light.

Edit: display is diy with no optics, frag tank is a chinese knock off of the reefbreeder budget light

 

[Webmanny]

Fwiw, Mr postal measured my tank with the club's meter and u,see 78 3w less he masured ~100 near the surface and everything we have, sps, lps, softies all grow great for us. My frag tank looks just a sbrigh (again, hardly scientific) and measured in the 300-500 range. In than tank I ha e so.e palys that are in an area that measured well above where the display tank measured and are reaching for light.

Edit: display is diy with no optics, frag tank is a chinese knock off of the reefbreeder budget light

Awesome. This makes sense. If you are getting 100 at the surface and growing SPS, I am going to need to start these off at a low percentage to make sure I don't burn my corals.

Thank you for sharing.

 

[Safir]

Montis grow great for us about mid tank, acrid are hit or miss but I contribute that to husbandry more so than light.

As always, I would recommend starting low and observing your livestock then adjusting as needed.