I think it differs with the distance of the led fixture, I've found it to be alot though. On my 3gal I ended up frosting the acrylic with spray paint to diffuse the light and it helped.
I guess my question is... is this normal with LED's? (MH shimmer times about 10)
I'm running all led's even on the fuge.The shimmer is crazy,your not looseing it.LOL I use plexi glass lids and it cut's the wall shimmer to zilch and the tank shimmer is close to the MH I use to run.Hope it helps.