Hook up the UV! Both of them, inline, then run about 1000GPH through it. Your water will be CRYSTAL clear, and the water that passes through the UV will have all algae spores/cysts killed, meaning fewer spores to grow on your glass or rocks.

I can't comment on the Bio Pellets as I have no experience or research to go on.

I am HUGE fan of UV, and will be adding it to the next system that is in process now. (Probably 57W again.)