In summary, BFT water with a low initial TSS concentration transitioned to a phytoplankton dominated system whereas water with a high initial TSS concentration remained a bacterially dominated system. This divergence resulted in changes in water quality variables over the course of the experiment that differed between treatments. The ability of the biofloc system to biotransform ammonia-nitrogen was retained at low winter water temperatures and in the absence of sustained TAN input in both treatments,although this really is of minor importance because fish are not consuming feed and excreting ammonia. What is important, though,is that the capability to biotransform ammonia without a substantial lag is retained once feeding resumes. High biomasses ofmarket-size channel catfish were maintained through the winter with high survival and in good condition in both treatments. Netyield was negative in both treatments, but might have been positive had feeding begun at a threshold temperature of 10◦C in stead of 16◦C. Having an active biofloc in the spring obviates the start-uptime required to establish a new, fully functional biofloc and the associated TAN and nitrite spikes. Of course, an economic analysis would be necessary to determine the costs and economic viability of maintaining the biofloc through the winter.