This model calculates the trajectory of a rotating tennis ball. In addition to drag and lift, the friction-induced decrease in rotation is also taken into account.

Video: https://youtu.be/f-8nRnLB9mg

The model was first used in the 1960s to determine the phosphorus concentration in lakes and reservoirs, for eutrophication assessment.

In this adaptation, s (sigma) is the oxygen consumption of 1 fish in g ind-1 d-1 and N is the number of fish.

Aerator functionality was added to the model, oxygen input can be adjusted by changing the aerator power rating. This would be an extra term in the equation. The aerator model is taken from Boyd - in the real world, if DO in a pond or tank is above saturation, there would be no aeration to save mony.