A couple of months ago
I started playing around with some designs for a device that allows me to dose small amounts of concentrated liquids, like Flourish and Flourish Iron.
While my powerhead dosing works great, it two disadvantages: the mixtures degrade somewhat over time, and (therefore) need to be replaced/refilled regularly.
So I spent quite a bit of time and parts to figure out a simple, cheap, reliable and repeatable design for this "Fluidoser"
It is still not 100% finished, but I have 4 or 5 of them running (dry, but fine so far).
Here is a step-by-step instruction if you want to try one or a few of these.
First, here is what we need:
- a mechanical timer
- some syringes (more about that later)
- plastic wire clamps the size of the syringes
- a couple of screws (I use #4-40 x 1/2")
- two check valves for each doser
- some plastic T's
- zip ties
- something to attach to the timer to hold the syringe (I use paint stirrers from HD)
- a little piece of drip irrigation hose or some sort of washers
- (not shown) some airhose, I am going to use the "mini" kind to reduce the amount of fluid remaining in the hose
Okay, now that we have everything, we need some basic tools:
- screwdriver for the screws
- drill with drill bit ( I needed a 3/32" for the screws I used)
- if you have a Dremel it helps to shape the paint stirrer
I guess that's it for now. Here is what we do:
1) Drill some holes into the rotating part of the timer. The more distance to the center, the larger will be the amount of fluid dosed. You need only one hole really, but since you are at it add some more in case you want to adjust the dosing later. Right after drilling a hole I screw a screw into it, carefully... if you do that gently, you won't need any nuts, as you are cutting a thread into the plastic.
2) Cut a piece off the paint stirrer (or whatever you choose) and shape it so it can be attached to the timer. Drill two holes through it, then through the timer, and attach with screws. See 1) about the screwing part.
I haven't done that for the smallest of my syringes, but I probably will. I attached the smallest one directly to the timer, however, the tilting point is so close to the rotating part of the timer that the top of the syringe moves around quite a bit throughout the day, therefore you'd need a little longer, flexible airhoses.
3) Take the plunger out of the syringe, and, with a hot knife, burn two tiny holes into the end part to pull through a zip tie, which then attaches to the screw on the rotating part of the timer. While you are looking at the plunger, give the rubber seal a nice massage with silicone lubricant. This will make the movement smoother, easier on the plunger and timer.
4) Drill a hole into the wooden extension, where the clamps with the syringe goes. I am using a piece of irrigation tube as a washer to lift the clamp up a little, so the plunger can move freely and parallel to the syringe.
As for the position of the hole, you need to see that the syringe is completely closed (no liquid in it) with each rotation of the timer. The clamp should grab the syringe towards the top, where the needle would go, to reduce the movement of the syringe.
That's pretty much it, wow, only 4 steps... Screw it all together and see how much the plunger moves (how much liquid is moved each day)
Regarding the syringes: I have a small one that doses up to 0.5 ml daily, one up to 3 ml, and one up to 6 ml (which I am not going to need for my tanks). The small one will be dosing Flourish and Flourish Iron in my 10gal tank, 0.4 ml daily*, there will be one ml of the mixture going into my 36gal, and 2 ml daily into my 100gal tank. Once it works perfectly I might dose PO4 the same way, with a second timer per tank.
* Please note that I mentioned these numbers just as an example... everyone doses differently.