You may want to add the Cacti and Succulents forum as the poster ewwmayo has some good posts such as this...

https://www.gardenweb.com/discussions/3482922/artificial-light-spectrum#n=49

tj

You say you have a grow light that specifies PAR (units umol/m2s). Leafy greens and starting plants need about 200-300 spread over a square meter. Fruiting veggies need about two or three times that. So if you have a 300 PAR lamp, you can hang it half a meter or so above a square meter of leafy greens or seedlings and be good to go. You'd need to be lower (and illuminate a smaller area) to get tomatoes to fruit. Google "PAR, plant light" to learn more.

Thanks! Here is the light I have. Chart says I get 297 umol/m2s at 30". Does that mean 297 PAR? This stuff is all brand new to me so thanks for your help!

https://www.amazon.com/gp/product/B07JZ3RKRF/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

Yes, PAR is "photosynthetic active radiation", which is a light intensity. Sort of like lumens, but lumens are for visible light., and PAR is biased to colors of light that plants need. 297 umol/m2s at 30" means that light fixture will grow a square meter of seedlings or leafy greens if the light is 30 inches over the plants (297 PAR). Put it at half that distance, and you might be good for a quarter square meter of fruiting tomatoes, if you could fit them underneath.

Thanks!