Normally I am not a big fan of these things, but upon doing lot of leg work and research on them,I believe they have a foundation to work if done properly. so the concept follows the same principle as carbon dosing like vodka/vinager/zeovit and so on (all of which I have issues with) but the thing that separates them from those is that the carbon source is in a solid form. What this does is to make it so you see what the carbon pool is where as with the liquid you have no idea, that and the liquids are broadcast into the tank where as the pellets are isolated.
Ok so what they do is to follow bacterial redfield ratio, which is the bacteria will use 50 parts carbon in order to bind 10 parts Nitrogen and 1 part Phosphorous. So the pellets provide the carbon and the bacteria take the N and P from the water column. I'll buy that. So most of the pellets you see are made from the same manufacturer and have the same properties, so corn syrup, or something similar, as long as they are PHA's their are all the same. So what you have to do is to keep the pellets tumbling this will keep them aerobic, if the flow is to slow they can go anaerobic and create all sorts of uglies like sulfides, methagenes and so on.
You must also start very slowly, so like a 1/4 of what they say to start with. What happens is that bacteria can be pretty efficent when given the carbon they need and whith out the things that slow the process, so ramp up slowly.
Also keep an eye on everything else in the tank, as they also consume oxygen they will be competing for it with our fish and everything else in the tank. One last one is that IMHO the reactor where the pellets are should feed right into the skimmer, this way once the bacteria have bound the nutrients you can remove them from the tank and thus have a positive export system. Give the reactor a shake when you see a heavy bio-film form on the pellets as this will keep the pellets aerobic with a small amount of anaerobic zone around the surface and it will allow you to export the bio-film that breaks free.
Oh one more thing, the ratio I put above, remember all three have to be present in order for it to work, so if their is no P they the N reduction stops, the same applies for all of them. Alot of folks end up with no measurable P but still have an amount of N left, this is the result of what I just explained.
anyway hope it give you an idea of how it works, now its up to you to make the call.
Mojo