Mars hydro fc-6500, blue and red light supplement

don't go back in time on lighting tech, move forward. get a full spectrum white light as it offers more and does better. You can get different temperatures or kelvins of white light. and some have far red added into the mix. The old school tech of blue/red leds only is based off of some flawed research stating they only use ble/red photos for photosynthesis but we now know this is not true. they are sometimes called a bluprple light as the two colours mixed make purple. UV is a bit of a gmick and not needed for indoors. plus it degrades things, you want to stay far away from UV-C.

supplementing with UV is not going to stimulate a lot more THC, but will increase volatiles like others said, already in your light...if you can do some programming on the app then do it, if anything a dedicated red to play with night transitions but really this is for folks without lights built in the last decade

Your lamp basically has everything it needs but in late flower you can ad a strong uv-a or uv-b lamp. This will stimulate a lot more thc production

You are using a full spectrum light. Your light already had red and blue.

Hey 👋 Honestly, you've chosen a competition-grade lamp 😉 It will do the job without needing any help! You could possibly add LED strips along the sides of your tent, starting from the bottom: they consume almost no power and will save you from having to defoliate for the lowest sites. enjoy !

Modern LEDs like your Mars FC-6500 have all the red and blue wavelength your plants can use.........adding extra won't make a measurable difference to your plants, but will increase your electricity bill. You are better off getting the health and feeding of your plants absolutely correct for maximum results. Without correct feeding, everything else you do won't compensate or cause magical results. Well thought out LST and no defoliation will also increase yields.

your grow light already has spikes in the red and blue wavelength ranges, despite it being white light -- aslo some 660nm reds, i'd assume.. some sort of red diode is mixed in. adding more is fine.. probably won't make a difference in any way that your eyes can discern. is there a measurable difference? Maybe.. depends on context a bit too. This will increase the DLI, so you may need to adjust height or dimmer so as not to give too much light, if you were already maxing out DLI. more photons in par/epar will raise your DLI on top of what the fc6500 provided. So, just keep an eye out for light stress.. make sure your node spacing on new growth is what you expect to see and adjust based on that.