PAR vs PUR

[LgTas]

So I have three tanks: 50l softy (cheap amazon reef light), 100l macroalgae and a 340l mixed reef (2x zetlight ufo's).

For the macro algae tank I've been using a cheap 7000k LED unit that I previously had on a planted tank:

Sunsun 78cm-95cm Length Adjustable Aquarium LED Light Fish Tank&Plant Lamp | eBay

Bulb color temperature 7500K, nature and comfortable, suitable for both plant and fresh water tank. Plant Lamp -. Stainless brackets length adjustable to fit your tank perfectly. Tank length: 780mm-950m.

www.ebay.com.au

When I measure PAR and PUR with my seneye (I understand that the PUR reading is not super accurate on these units) I get the following readings at the centre mid point of each tank:
50l - PAR 170, PUR 81%
340l - PAR 190, PUR 83%
100l - PAR 280, PUR 63%

My first question: is it as simple as PAR x PUR% = usable available photosynthetic radiation?
e.g. for the 100l - 280 par x 63% = 176.4

Second question is linked to my surprise that such a cheap LED could put out so much PAR. So it's clearly powerful enough but I can see that on the PUR graph it has no ultra violet output. Basically just hitting the blues, greens and reds. The LED spread is mostly white LEDs with a few blue LEDS here and there. Given the low PUR % and absence of the violet spectrum, would this light be sufficient for BTA and rock nems?

 

[Nano sapiens]

So I have three tanks: 50l softy (cheap amazon reef light), 100l macroalgae and a 340l mixed reef (2x zetlight ufo's).

For the macro algae tank I've been using a cheap 7000k LED unit that I previously had on a planted tank:

Sunsun 78cm-95cm Length Adjustable Aquarium LED Light Fish Tank&Plant Lamp | eBay

Bulb color temperature 7500K, nature and comfortable, suitable for both plant and fresh water tank. Plant Lamp -. Stainless brackets length adjustable to fit your tank perfectly. Tank length: 780mm-950m.

www.ebay.com.au

When I measure PAR and PUR with my seneye (I understand that the PUR reading is not super accurate on these units) I get the following readings at the centre mid point of each tank:
50l - PAR 170, PUR 81%
340l - PAR 190, PUR 83%
100l - PAR 280, PUR 63%

My first question: is it as simple as PAR x PUR% = usable available photosynthetic radiation?
e.g. for the 100l - 280 par x 63% = 176.4

While I've never used a Seneye, your interpretation is correct as PUR is a subset of PAR. The PUR % would be useless without something to take a percentage from (PAR).

Second question is linked to my surprise that such a cheap LED could put out so much PAR. So it's clearly powerful enough but I can see that on the PUR graph it has no ultra violet output. Basically just hitting the blues, greens and reds. The LED spread is mostly white LEDs with a few blue LEDS here and there. Given the low PUR % and absence of the violet spectrum, would this light be sufficient for BTA and rock nems?

Back in the day, early LEDs with limited (or no) violet/hyperviolet could grow coral and other photosynthetic organisms. Later arrays started to use violet/hyperviolet LEDs in more substantial amounts to more closely mimic the more complete V/HV light spectrum of MHs and T5s.

You can see on the graph below the A and C chlorophyll peaks:

You can see that 'Royal Blue' (~450 nm) provides a fair amount of both Chl A & C. Hyperviolet (~420) provides additional Chl A mostly and should provide better results for coral in the appropriate amounts (some potential pigment enhancement and especially growth). ~470 nm 'Blue' hits the Chl C peak. ~670nm 'Deep Red' hits the secondary Chl A peak, but too much of these red wavelengths can have negative consequences so most go light on red (and some even have no red wavelengths at all).

There's a lot more to the complex ways that coral and their zooxanthellae interact with light, but I hope this answers your question.

 

[LgTas]

You can see on the graph below the A and C chlorophyll peaks:

You can see that 'Royal Blue' (~450 nm) provides a fair amount of both Chl A & C. Hyperviolet (~420) provides additional Chl A mostly and should provide better results for coral in the appropriate amounts (some potential pigment enhancement and especially growth). ~470 nm 'Blue' hits the Chl C peak. ~670nm 'Deep Red' hits the secondary Chl A peak, but too much of these red wavelengths can have negative consequences so most go light on red (and some even have no red wavelengths at all).

There's a lot more to the complex ways that coral and their zooxanthellae interact with light, but I hope this answers your question.

Amazing, thanks! I'm going to re-measure tonight and compare to your graph to make sure I'm hitting the right peaks for Chl A and C while not overdoing the reds.

 

[Dana Riddle]

The Seneye is an amazing device considering its price. PAR x %PUR = PUR is a rough estimate of the 'value' of light quality. However, PUR is of secondary importance (when using lights made for reef aquaria), so if PAR is of 200-300, your nems should be fine. But don't forget the importance of water motion.