The dosing pump is very much a home-made thing (and it also requires a proper mounting enclosure!):

It currently consists of:

• Silicon tubing
• Peristaltic pump
• Outdoor electrical box
• A 3D-printed bracket I made in Fusion 360 (file can be found in main project page)

There was already an ozone venturi injector for the pool, so I am tapping into that to inject the bleach. My 3D printed design attempts at a small venturi injector of my own were all unsuccessful, maybe because I tried making them too small.

No specs are provided on the stepper motor, and I don't really trust the stated 1.3A rating, so the board is designed to run it at around 500 mA. I can get about 100 mL per minute, which isn't very much, but works well enough.