El Cheapo dosing pumps

 I like to automate things on my fish tank, and decided I wanted to automate fertilizing my aquarium plants. That led me to the seedy underworld of dosing pumps. I really wanted to stick with a simple straightforward...and cheap one. A dosing pump is connected on one end thru tubing to a liquid fertilizer, and the other end pushes a few ml a day of the plant fertilizer over the edge of the tank into the water. 

 I got a Jebao DP-4, and tried a couple of things to get it to work. Warning: unless you are fiddling with aquarium doing pumps, the rest of this post will be a snoozefest.

I found complaints online that the DP-4 dosing pump leaked air into the line, meaning that it would dose inaccurately. So I bought slightly small silicone tubing thinking it would make a better seal. It didn't. It both leaked in air, and the silicone tubing I got was even pulling air in thru the silicone walls! I didn't realize silicone tubing could be semipermeable like that. So I got airline tubing from Aquarium Coop, which isn't silicone,and that helped a lot.

The other complaint folks had was the tubing didn't seal well in the pump head, meaning the plant fertilizer left in the tubing slowly leaked back into the fertilizer bottle. I verified I was definitely seeing this in my dosing pump. So I found a few videos on flipping one of the parts around, and it totally fixed it for me! Here's the before and after pics.



I tested it by calibrating it to 100ml, then having it sit for several days, and then rechecking the calibration. It was within 2-3%. Which should work for me.

I also wanted to mix my own fert for cheap, and start with raw ingredients so I could tweak the recipe if my tank needed more or less of a particular thing. So I bought a set of powders, and mixed up a batch of macro and micro ferts. I diluted it by half, so I could dose double the ml of liquid each day (the dosing pump is not as accurate with tiny doses).


Today I finally got it all set up and tested with my dosing pump, and I'll see how the plants respond.


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