I have the SpinStream nozzles on my tank. Occasionally they will get jammed up with calcium carbonate and stop spinning. This was happening to me every 2-3 weeks for a while, but now it hasn't happened in the last two months so maybe my water conditions were off before (CaCO3 shouldn't be precipitating out of the water if everything's balanced correctly). Either way, when it happened I would pop them off and submerge them in a glass of pure vinegar for 15 minutes or so. Then I'd blow through them which makes them spin, the remaining chunks of white gunk would fall out, I'd rinse them in water and pop them back in. I get much better "random" flow in my tank with them than I did with the fixed nozzles.
I would be curious to try the fixed random flow generators from Vivid Creative Aquatics, but since I already dropped $50 on the SpinStreams, I have a hard time justifying it...