SEAOURA 24/7 LED Aquarium Light for 30-36 Inch Fish Tank, Auto On Off with Timer, 9 Colors, Adjustable Brightness, Daylight Moonlight Mode, Full Spectrum Fish Tank Light for Plants

I don't think 20 watts is gonna cut it. I have a 20g long so it's only 14 inches high and my light is 56 watts. It's this one from the same company: https://a.co/d/03fACE38 So mine must be a model and size up from the one you're looking at, but mine in your size would be 36w, quite a bit more power.

https://www.amazon.com/dp/B0DQTQ69KQ/ Their plant light is finally on sale since they increased the price by $10.