I posted earlier on the Next Reef SMR1. I researched this subject too before purchasing, and yes the next reef is a little more bucks....but FWIW, here are my specs...180 reef tank, 40 gall sump/fuge. I run BRS Carbon and GFO and 1000 ML of Ecobak pellets. The SMR 1 is powered by a maxijet 1200 fully opened. I believe you want a gentle tumble, and not a vigorous tumble. I have seen at LFS that sell the pellets and different reactors, and look at their displays and it is obvious the reactor are not reducing nitrates like they are supposed to and I suspect it is because the tumbling is either non-existent or way too fast.
Also, very important, but never really mentioned....The pellets must have a catalyst or a 'food' source.....I dose bacteria (zeo bak) twice a week (one time in tank directly and once in sump directly near intake of bio pellet reactor). I started the reactor from day 1 of tank set up (set up 12/25/10). Yesterday's parameters reading zero nitrates and zero phosphates (both high and low end readings). I have a sps dominant tank with many aquacultured (ORA) and wild colonies and frags and everyone seems happy. I do have a small fuge in my sump where i have 10 llbs of miracle mud and grow cheato, which for sure also helps with nutrient export (I cut back my cheato big time yesterday).
Last, I feed COPIOUS amounts of food to the happy fat fish my tank (4 Tangs, 3 Chromis, 6 Anthias, 2 Cardinals, 2 Dartfish, 3 firefish, 1 fat mystery wrasse).