The number of filters depends on the max pounds of fish and the surface area of the media in the clarifier. I sized my filter using the following information from the SRAC article I post earlier:

10 grams/100 pounds of fish/day
Ammonia removal rates may range from 0.02 to 0.10 grams/ft2 of biofilter surface area/day

Assume the worst case scenario of .02 grams and then use 1 lbs of fish per 2 gallon of water in the tank to be on the safe side.

(lbs of fish / 100) *10 = bioload in grams

then

Bioload/.02 = ft2 of surface area required

ie 2500/100*10=250 g ammonia
250/.02=12,500 ft2 of surface area

So you would need 12,500 ft2 of media. Media is usually rated by surface area per ft3. Sand is 7800ft2 per ft3, lava rock is 16 ft2 per ft3, I have no idea what Deer netting would be.

55 gallon drum can hold 7.35 cubic feet of media when full.