Mine grows under 2 T5 HO lights in winter. They are on for 12 hours and the plant is maybe 4 or 5 inches from them. They do have a reflector hood which likely distributes the light well. You can buy the T5's with reflectors now also if they are the SunBlaster brand. A grower who came to speak said he feels that with the reflectors, you maybe get another 50% more lighting than without. The silly little reflectors are sure expensive tho.

Believe it or not, there's a phone app for that! I use Galactica Luxmeter.

I think more is always better with this species.

Thanks Silken!

It looks fabulously healthy, with lots of good roots. The color appears a correct light green, indicating good light.

Is each new growth substantially bigger than the previous? If not, I would suspect inadequate feeding, or too-low temperatures.

If you have an old SLR with light meter, you can calculate foot-candles. Aim the camera with f stop 8 at a white piece of paper. Note the exposure time. Look it up on a table I'm sure you can find somewhere on the Web. I don't have it with me but I might remember to look for it later.

Phone apps won't work well unless the developer knows the specs for your specific phone camera light receptor.

Really!!! Hmmm. Thanks!

---------- Post added at 01:58 PM ---------- Previous post was at 01:50 PM ----------

I just checked, my phone is not compatible. :(

You certainly inspire confidence in this one. The roots are new, I added kelpmax a month ago and they went nuts after that. I'm happy they reached down into the leca and kept growing in that direction. Since then I have been feeding weekly weakly. Something I neglected to do thus far. Also the room it is in can get pretty cold at night, but only recently, not during the summer. I did notice one small leaf is turning red, possibly cold damage and signs of malnourishment? Thanks for your opinion!

Red Catt leaves is often a sign of strong light exposure. Without fertilizer, Catts in most media we use will hardly grow.