Turns out the setup is too good to be true. The towers don't house permanent
denitrification colonies, and the BioMagic seems capable of crashing a cycle. Miyamoto's tank has been building in nitrates, so as a test of the BioMagic, I put some back in the tank. The cycle crashed within days, and the
ammonia rating shot up (a danger of an overstocked tank).
Sirdarksol's final opinion of the Hi-Q product: If you use it as directed (putting the additives in every week, and changing the filter media out every month), it will reduce the need for water changes to lower nitrates (but won't do anything for other dissolved organics). Without the additives and filter changes, the system is a pretty good filter, but won't do anything for your nitrates. Lastly, never,
ever add BioMagic to an established filter without using the special carbon filter pads (which soak up excess ammonia).