A Stingray LED light is definitely marginal for a 18 inch high tank. It works well on 12 inch high tanks, but the light intensity drops pretty fast at the longer distance. However, I think a Planted Plus would be too much light. A Planted Plus 24/7 light would work OK because you can adjust the brightness down to whatever level you want. Finnex no longer provides PAR data for their lights, and a standard Apogee PAR meter doesn't give as accurate a measurement of PAR for a light with significant red light in the spectrum, as it does with fluorescent lights, so most of the PAR data we have on these newer Finnex lights is just approximate. In other words, I don't know for sure how much light you would get with any of those Finnex lights. For now, I think I would just wait another month or so to see how this setup works out.