Hey Jubs, thanks for asking, I have this working on almost all my tanks at the moment, still refining some of the details.
The challenge is to find check valves that can handle the extremely slow flow, while not allowing a siphon to drain the fertilizer bottle too quickly, or fill it full of water.
I use this in connection with the water pump method. The Liquid-doser injects the micros into the airline that goes from the macro container to the tank, and then once a days the macros get pumped into the tank, taking the micros along on their journey.
Right now I fill the bottles with enough Flourish to last for four months. Then, after 4 months, I check and see how much is left. If there is too much remaining in the bottles, I need to increase the dosed amount.
I need to take a picture of a more recent version. It's a bit simplified, where the plunger is directly connected to the timer wheel, and the syringe itself tilts.