hoppycalif

Yes, several years ago I was trying to convert "high light", " low light", etc. to PAR numbers, measured at the substrate level. But, as time marches on, my memory isn't what it used to be, and I don't recall the numbers very well now. My interest is now only with relatively low light tanks, so all I do is try for 30 PAR units minimum, but not above 50 PAR. I know even 20 PAR can grow some plants, but I think 30 is much better.

Light intensity is never simple. For example, a lot of light reflects off the glass to air interface back through the glass and into the water, but only if both sides of the glass is very clean, which isn't normal for me. If I measure with a PAR meter in the water, at the substrate, there is a big difference between very clean tank and normal tank. So, which condition should be at 30 PAR???

And, just to add to the complexity, for years Apogee did not recognize that their PAR meters were giving incorrect readings in water, because of the water to PAR meter sensor interface was not allowing 100% of the light to get to the sensor. I spent over a year trying to make a DIY PAR meter from a Lux meter, but gave up because I saw the effect of that loss of light and assumed it was a problem unique to me, one I wasn't able to avoid. I was shocked to find out that Apogee was finally acknowledging that their meters also had that problem

davemonkey

Thank you, both, Michael and Hoppy. This is extremely helpful information.
Sorry for hijacking your thread, Darren. But if I know you, you were probably thinking likewise.

mudboots

All good. So I went with the "Fuge Ray Planted Plus" which is a little less high-tech than the other Planted Plus. I think it gives moderate lighting but did not measure the PAR. I have my moonlights on with the regular lights, and just have them on a timer. 2 fixtures and they come on 30 minutes apart for 8.5 hours each for a total of 9 hours run time for the tank.

I am not using a "soil" substrate and am only adding small amounts of supplements (mirco nutrients and potassium, and a little excel for carbon), so I don't anticipate rapid growth. But my algae is definitely in check, so evidently I guessed correctly on what to mess with and the light fixture to use.

This may change when I finally add the Apistos and the cories...will have to adjust as I see issues pop up.