recirculating is the only way to go really. I dont use biopellets because they were too difficult to manage. It either stripped the nitrates and not the phosphates, or it stripped both too fast and made the coral look horrible. It was really difficult for me to find the right amount to use on my tank, and I honestly didnt really need it, I was just trying it out. The reason I say recirculating is the only way to go is because you actually have control! see, the classic biopellet reactors (the one I used) had a constant and very fast flow that kept the biopellets moving. This also cause my water to come into contact with the biopellets at a really fast rate. Once you have an established bacterial population, it becomes very effective at stripping the nutrients out of the system. The really fast water rate and the extremelly efficient bacterial population causes your nutrients to be depleted waaay too fast. The recirculating reactor provides high flow within the reactor, which is needed for the bacteria colonies to grow and thrive, while also allowing you to control the rate of water comming in and out of the reactor. This allows you to control the rate at which your water comes in contact with the bacteria within the reactor. If I had the money, id give it another try using the recirculating reactor. I'll probably incorporate it in a different system because I have mostly lps and they need a slightly more nutrient rich environment. That's just my two cents though