you are doing very well, your dog just had a good feed :slfg:
I don't know whether you'd call it light or UV or both. There is light that gets through thick net curtains, and through the frosted glass pane of the door. The tanks are well back from where you can see the lighted area hits the carpet but it's obviously still enough to get the algae going. I also note that these tanks have their lights on for about 2-3 hours a day only, from around 5pm, and they have 6500k bulbs. The other tank I have that doesn't get that algae has a 6500k bulb and a 14000k bulb and is in the same area but doesn't have a pane facing the light so much.