Maybe I'm just tired, but the grit that is spec'd for the Birdman Sand & Gravel filter, what type of sand material is preferred? Is it ....
Poultry Grit or Chick Grit
The former I can find in 25 lb bags. The later I can only find in 5 lb bags.
The chick grit is probably 1/4 to 1/2 the size of the poultry grit. Chick grit is smaller than rice, poultry is larger than rice.