No disco effect at all, why I like them and the nicrews. The problem I have with the nicrews is the spread, I have a long tank. I can mount them higher but the light spill is just more of and issue. You get some shimmer if you have some current on the surface of your tank, but I'm not a fan of the Kessil and for me noopsyche disco effect, some like and some don't I am in the camp of do not like it...What is your mounting height? These are the 90 degree versions I was debating on buying. Do you get any disco effect?