When using LEDs, what constitutes "high light"?


Junior Poster
Oct 5, 2013
Newbie question here ...

I'm following Tom's guidelines and doing my homework, but before choosing a method I want to follow it is clear I need to understand how much lighting I am really working with. There is a TON of data when dealing with fluorescent fixtures or metal halides, but I'm using LEDs which clearly seem to be different.

I purchased a 24" Current USA Satellite Plus PRO, which is supposed to be good for "high light level plants" (according to the manufacturer, anyway). Since I don't have a PAR meter, I am going by the manufacturer's specs, which claim the unit puts out 30 Watts and 2,000 Lumens, and has a PAR value of 100+ at 12" water depth.

I have a 40 gal tank that is quite deep (15" from surface to top of substrate) and the light is 7" from the surface.

While I'm still trying to nail down which method I will follow, I am currently using CO2 injection, and my drop checker shows a consistent 30 ppm. I've also cross-checked this based on my alkalinity (6 degrees) and pH (6.8).


1) I see lots of recommendations on what PAR level I need to produce, but I am confused as to where to measure that. It makes sense that one would measure this at the substrate for low-lying foreground plants, but I also have things like Wisteria and Amazon Swords which grow quite tall - for these plants wouldn't it be more relevant to measure the PAR level at the depth where the foliage occurs?

2) Is there a simple guide that lists the required PAR levels for each species of plant? I see that this is listed for the few species that are in the "Plant Database" on this site, but only shows a few entries. Is there another resource I should look to?

3) how reliable are the manufacturer's stated performance figures for PAR levels? Can I use the data provided as-read, or is there another resource I can use that provides PAR levels based on independent testing? I found a few videos of this on YouTube, but not sure how reliable the sources are.

Any thoughts would be appreciated.

Dale Hazey

Junior Poster
Feb 18, 2017
Manufacturer claims about performance are probably sugar coated

Rotalabutterfly.com Has a light calculator

Tropica.com has some detailed information about individual plants

I have read here many times that low to medium light, and good co2 is the way to go. When you step up to high Par and push the envelope theres a better chance to crash.
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Lifetime Member
Oct 3, 2013
Albuquerque, NM, USA
I started out with a 40 breeder running a Current USA Satellite+ -- this was before they introduced the +Pro. I believe their PAR claims, I suspect I was getting about 30 umol at the substrate. It worked well for the staurogyne, mosses, and java ferns I was growing at the time. I tend to think that a manufacturer would be dumb to do anything other than report actual measured values from a sampling of their products.

I wouldn't necessarily trust the light calculator, the assumptions it is based on seem like a stretch at best. So many things (components, reflectors, ballasts/LED drivers, etc) affect the lighting efficiency of a system for the amount of power put in, it's a REALLY difficult thing to model compellingly.

Ultimately, I think the light you've chosen will work well for anything you'd want to grow -- don't overthink it! The most typical assumption we see around here is

"I want to grow plants, so I need ALL of the light! ALL OF IT!!"

I bet you'll do best running that Satellite +Pro at 60-70% for starters. There are relatively few plants that require more than that.


New Member
Jan 13, 2021
Ashburn, Virginia, USA
Hi....I'm not anywhere near expert level, but I think it makes sense to have the par level for high light at a lower level because high medium light without CO2 can be really problematic. According to Tom Barr, many nature-style tanks have around 50 micromoles of PAR at the substrate, yet they can still grow "high light" plants.


New Member
Jan 10, 2021
Yeah, a majority of the newcomers I see here and elsewhere want crazy high light, thinking it will make their plants grow better. Your better bet is to have just enough light to get your plants to grow the way they are naturally supposed to. A great majority of plants will get by with 50 PAR or so, and more than that is just going to drive algae. When you are more familiar with the various aspects of your tank, you can start to increase light to get some of the more dramatic tanks you see on this forum.