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Discussion Starter · #1 · (Edited)
I finally replaced the light on my 20g tall after the old one broke a couple months ago. I'd been making do with a nano tank light so I could see my fish, but was reduced to just keeping some java fern and cryptocoryne in the tank due to the seriously inadequate illumination of the temporary lighting arrangement.

My new light is a Beamswork DA FSPEC 24", which claims to put out 3600 lumens.

I've no idea how that converts to PAR, and I'm still slightly fuzzy on the nuances of PAR ranges anyway.

The tank is a standard 20g Tall, so it's 24" x 12" x 16" (60cm x 30cm x 40cm, 72 liters), and the light brackets raise it roughly 2" (5cm) above the rim.

I'm happy with the fixture, but I want to figure out how it ranks in terms of low-med-high lighting, as that will govern the range of flora I'll be able to utilize to replant it, and also whether it's worth finally looking into investing in a small co2 system to grow more demanding species.

Edit - In case this is pertinent, the nodes & colors are as follows: 39x 10000k, 12x Actinic, 4x Red, 4x Green

I also found a calculator for lumens per liter, which put the light at 50 lm/Liter. That sounds good, but I'm also finding info that states that lm/Liter isn't a particularly good way to tell if the light is adequate for growth... Help.
 

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The da fspec is actually pretty bright at those depths. You can put together some very rough estimates of par readings by downloading the Lux Meter app for your phone, taking a reading, and then dividing by 80. This will give you a VERY rough idea as to par. But bottom line is that in a low tech tank you might want to consider buying one of those inline dimmers that work the beamswork lights.
 

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Discussion Starter · #3 · (Edited)
I'm not entirely sure I'm doing it right, but holding the phone next to the tank at the depth of the gravel gave readings of between 150 and 197 (so that would be PAR around 2ish?).

Mid-depth of the tank shows about 315 (PAR around 4?).

Just below the fixture gave a reading of 13,000 (PAR 160?).

I feel like this would be much more accurate if I had a submersible sensor. The tilt on my phone next to the lower part of the tank caused pretty wild fluctuations in the reading.

Edit: since I had upgraded my 60g light too, I decided to try reading the lux on that tank as well. I got very similar ratings at gravel line and midpoint on that one, so presumably that means my 60g is running fairly bright as well now?

Second Edit: I found a website (Aquarium PAR Data) that shows a range of 60-70 (offset of 6" to 0") at 15" depth for that fixture in their tests.

I'm so confused now.
 

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i have the same light on the same tank. i would say it's high. i have monte carlo growing at 80% at 16.5"; par of 60-70 at 15" seems about right. there is a thread in the lighting forum that gives da fspec par and pur values (but for longer fixtures).

get the beamswork rise/dim/timer. you can dim the light, use sunrise/sunset ramping, and timer.
 

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Discussion Starter · #5 ·
i have the same light on the same tank. i would say it's high. i have monte carlo growing at 80% at 16.5"; par of 60-70 at 15" seems about right. there is a thread in the lighting forum that gives da fspec par and pur values (but for longer fixtures).

get the beamswork rise/dim/timer. you can dim the light, use sunrise/sunset ramping, and timer.
Awesome. Guess I have an excuse now to finally invest in CO2.

I do want a timer/dimmer for it. I had ordered one, but the connection turned out to be wrong, so I'll have to get one specifically made for the fixture.
 
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