I just got back today from Aqua Forest's gracious event and demo. I took my PAR meter and Ian brought his as well to the event. Every tank I measured, the one that ranked 20th in the ADA contest last year in the wolrd ranking had no more than 150 micromol at the surface of the tank right near the HQI MH light. At the bottom all along the front, 35-40micrmol and near the window at noon time(north face), 50-55 micro mol.
Gloss, HC, E tennellus, moss etc, no issues..............
This is very low light overall.
PAR meters do not care about brands, lux, lumens, funky nutty correlation tables, the water, reflections, distance etc, they can drop down and measure the parameter that makes the plant produce sugars via photosynthesis right at the surface of individual leaves.
Someone said "there is a redder plant, measure there", so I did: no difference.
On to other tanks, exact same trends, all very low, 30-50micromol ranges at the bottoms, 150 or so at the highest, did not matter if if was a 180cm, 120cm, 90cm, 60cm, 45 cm sized tank, all where pretty much lower light tanks in each and every case.
I was a bit mythed about the ADA lights, they are really inefficient or set up that way to limit folk's from going wild with the lighting.
Many think more is better, so reducing it down helps folks do better and have better luck with CO2, so many think the ADA lights are better.
But not when tested...........
Almost 1/2 of what my lights are at home.
How might this influence what folks think and assume about CO2 and stability?
How about nutrient demand and uptake?
If you cut the light by 1/2, what do you expect?
This was not some aberration, this was done in front of 50 plant hobbyists in the club here. I'm not pulling anyone's leg here with some baloney.
This was not merely 1 or 2 tank,s this was 7 tanks and other folks' I've gone to to measure had similar values and results.
I've heard about every crazed idea about measuring light that's out there, yet few have ever bothered to measure the one that matters the most in situ and compare. I have a bit more lately and the cost is not much now either.
I have 2-3x as much light in some of my tanks, yet I also have no issues, but much faster growth rates.
I also scale up the nutrients, and the CO2.
If you don't, then you have a lot of issues.
So keep light low, not high!
BTW, the T5's rock and produce some of the best light and are very even. I like them, but.......I like HQI and ripples light real sun light too