While my powerhead autodosing works pretty good, there are a few small drawbacks. One is that the solutions start to degrade somewhat over time. Second, every 2 weeks or so <gasp> I have to clean and refill them.
For $70 or so you can get the Liquidoser, which (probably) works great, but if I can help it I don't want to spend that much, plus it needs to be refilled too, plus it needs to be somehow integrated into the canopy.
Inspired by this ingenious invention by Dr. Ruben
, I went through my bins and boxes and found
an unused mechanical timer,
an oral syringe,
a T (actually an X, but I put a cap on one leg)
a check valve (need two though)
a metal angle
something to hold the syringe in place
screws and pieces of airline
Total value of parts $7 estimated.
Then I cut a piece of wood (one of those paint stirrers that they give away in HD), drilled two holes, and attached it to the timer. A little off-center, I screwed a screw which will be the driving force of this thing. The position of the screw determines the movement of the plunger and therefore the dosed amount. In my collection of unused parts, I found a plastic holder for heaters which I used to seat the syringe, instead of an U-profile which I did not have.
In the Dutch version, the syringe tilts to not interfere with the circular motion of the timer. I simplified this somewhat, using a wire that connects the screw on the timer to the plunger.
I can't believe it, but it seems to work! I have it set to dose 2 ml with each cycle. I was out of check valves, so I used one of my DIY bubble counters until I get another CV.
So now it is sitting there and thinking... I will let it run for a few weeks to make sure it works. Then, one just needs to stick the "in" air line into a bottle of Flourish (or whatever you put into your tank) and maybe give it a little shakey every month or so.
(Keep in mind this is still in beta, I will most likely change/improve this design. I might give the Dutch tilting version a try, to reduce the stress on the timer.)