Peristaltic Pump (simple & working) for an automated fertilizer

Plants need fertilizer. Manual dosing kept me doing to much or too little with results accordingly.
The pumps feed liquid fertilizer into the irrigation system while watering. Dosing can be adjusted on a very wide range.

A lot of peristaltic pumps can be found around. I tried a lot of them. Mostly I disliked the many parts needed and tolerances were not fitting for me. This thing consists of only three parts plus one optional mount bracket. To complete this pump only needs one NEMA17 stepper motor, 6 ball bearings, and 4 screws are needed.

Full explanation on hackaday.io:
https://hackaday.io/project/179235-fertilize-home-grow-the-engineering-way

This pump prints super easily. Tolerances were spot on for me using a Prusa MK3 with any (even super cheap) PETG filament.

Additional parts:

• NEMA 17 Stepper motor, 45Ncm strong enough
• 6 Ball bearings 695, ZZ type recommended
• 4 M3 screws with allen key head
• Silicon pipe external diameter 5mm

Update:
Unfortuantely every NEMA motor is different. On some motors I have seen that the notch is not long enough. The ball bearing mount will not go far enough into the pump base. Placing the optional spacer between motor and pump base should do the trick.

Update2:
After one year of usage the top most bearings holder got a little loose, bearings left the sweet spot. 
To fix that for rehappen I reinserted everything and added a tiny amout of CA glue on the shaft to finally fix it. Looking good so far.