PAR and PUR from a cheap LED bar


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Dec 10, 2020
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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:

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?

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