I got mine through the winter this way by putting 2 x 300 watt heaters with air stones in the tank for a 300 gallon tank. Shut the pumps off after 11pm and turned them on at 10 am. Fed lightly in the morning if temps weren't too bad otherwise did not feed at all while getting them through winter. This would only be worthwhile if you needed to get them through the winter to continue growing for another season. You will want some type of aquatic plant that will uptake ammonia directly. Duckweed and azolla work ok.