I use Excel in my 2 1/2 gallon nano tank, and haven't seen any pearling. The plants all grow, but slowly. For example I have a bit of R. rotundifola which is bigger than when I put it in there, but you can't see any day to day difference. It looks very healthy and has reached the water surface now. My light over that tank is a 27 watt PC desk lamp, about 6 inches above the water.