I just got 2 of the single BRS reactors. With 2 singles you'll be able to control flow to each one individually. They come with sponge filters in them but, like you said, they'll get plugged up and you'll have to keep adjusting the flow to the dual reactor to keep the GFO tumbling. With the single, it's OK if the carbon reactor loses some flow through it as this leads to more contact time with the carbon, but this won't affect the GFO, which needs the right amount of flow to keep it moving.