Foam on plastic lens polisher compound

[MIOPE]

We have a central unit where the polisher compound (for plastic lenses) is collected, filtered, chilled and send back to polishers.
There are moments in which foam is build on polishers and the central tank. Adding a gallon of new polisher will help. Would like to know what cause the foam and if there is a additive that can be used to reduce the foam.

[MikeAurelius]

DAC Vision in Texas has defoamer.

[Chris Ryser]

Any optical supply company that sells surfacing and polishing items will have a bottle of antifoam for sale. A few drops will do the trick.