[g8wayg8r]

Finally, I have a use for that old air pump in the basement.

I love this method and would use it over the gravity feed any day. That method depends on the head from the height of the solution in the container and it will vary greatly unless you have a reservoir like some of the ultrasonic humidifiers that keep a constant water level. That's way more complicated that the air pump method. Since the head for the air pump method is determined mostly by the run length of the tube from the bottle below the tank to the rim of the tank, the amount of ferts or water in the bottle is almost irrelevant. The dose rate should be relatively constant.

Simple, inexpensive and effective. Gotta do it.