Well I finally opened the free sample pack of his mini no carb veggie discs...and its the first food my silver dollars don't seem to like. They do love Ken's Spirulina wafers though and freeze-dried earthworms. I still haven't opened the brine shrimp/blood worms that I have from Ken's, because I've changed how I plan to stock the tank and don't have carnivores right now (except plecos).
After having time to review them, I wouldn't recommend Ken's brand replacement cartridges (for the emperor/penguin models). The frame is flimsy and after a couple weeks will dislodge from the slot it fits into, which then pushes against the bio-wheel and keeps it from turning, as well as not doing its job (water then passes BY it, rather than through it once it dislodges).
Sometime in the next few weeks I plan to order Ken's sinking Earthworm sticks and Brine Shrimp sticks (for my carnivorous plecos).