Thats part of the reason some people have problems with these. The natural thinking in the hobby is that "If you have cyano, the water is dirty." "Therefore, if pellets clean phosphates and nitrates, then more should work better, and take care of the cyano by cleaning the water." Thats NOT the case. Cyano is a bacteria, and as such, carbon dosing feeds bacteria. adding more pellets will only feed and fuel the cyano. Theres likely too much carbon being dosed already, and thats why the cyano is going crazy. The biopellets will eventually get consumed to a point where the cyano dies off, but why wait? Take out some of the food your feeding it.
Are they just tumbling at the surface or are they all in motion in the reactor? If its just the surface then I would pull some of the pellets out. Say a third of them to start. That should allow the rest that are in the reactor tumble better and make them more effective. I would also cut back on your bacteria dosing for a couple of weeks too. I don't think you need to keep dosing bacteria, the bacteria thats already there now should be able to consume the pellets and keep its own steady population going. Its a good idea at first, but not needed once things get going. Just wasting money really. I would dose some maybe once a month or so, even once a week if it makes you feel better but I don't think you need to dose it more then that with the pellets.
See how that works, give it a couple of weeks and you should see an improvement in the cyano. Then, when the pellets get low again, add the third you pulled out back in. Probably 3 months down the line.