The electronics stall in the Pyramid now sells bulk containers for plants, animal specimens and general merchandise, in both large and small sizes. The general merchandise container can hold rocks or any goods for resale.
What these containers really do is allow you to sell in bulk to Phibes, the trade shop, or in the greenhouse. Just stuff the containers with whatever you want to sell, then sell the container itself, and the buyer will automatically add up the value of everything inside and pay you.
So you no longer have to sell fish one by one, etc.
Just make sure to put the right goods in the proper container. Whoever you sell to will buy it, regardless of what is inside, so don’t accidentally stuff the animal container with rocks, or you’ll lose your rocks for a minimal price.
One or two larger canines should be able to carry the large containers, while the remainder of large-med size canines can carry the smaller ones.