This is now running for a couple of weeks, and doing okay. One thing I noticed is that if the hoses are submerged in water, the tank water mixes with the micro solution which isn't intended. If I leave them hanging out of the water though, the solution moves so slowly that the drops turn to a black gooey stuff with the flourish, and salt in the case of phosphate.
Solution - I will add check valves to the end of the hoses, and leave them submerged. We'll see how that works.
I think you may run into problems with gunk building up on and clogging the check valves causing them to stick either open or closed over time. I'd be very curious to know if this becomes a problem.