Introduction: Fertiliser Dosing Pump for Aquarium

In heavily planted aquarium with high light and CO2 addition, on almost daily basis I have to add liquid fertilisers.
Problem appears when I'm going on holiday (or want to sleep bit longer and there's no time in the morning to put some fertiliser before work ;-) ).
The off-shelf solutions are quite expensive, so I've decided to give a go peristaltic pump.
The choice I've made because peristaltic pump is probably the most accurate way for dosing liquids.

Step 1: Parts and Tools

I've bought used peristaltic pump from ebay. Its actually pump itself, gearbox 1:150 and DC electric 12V motor.
I also purchased electronic timer with the weekly schedule exact to 1 minute.
Airline enough to reach aquarium, and another small piece from pump to bottle
Rest of the bits and pieces I found at work/home:
There was 12V power supply from dead old netgear ethernet hub, and small pads/skid protectors again from the old hub
Small piece of aluminium angle bar
Piece of 5 mm plastic ~8x13cm
Pentium 4 air duct from ATX case ;-)
Bottle which fit inside air duct
Screws, nuts and washers

Step 2: Assembly

Basically nothing to say about. Put everything together (as shown on the photos) and keep it as tidy as possible, avoid sharp edges (sand all sharp edges). Make counter bore to hide screw heads, etc...

Step 3: Adding to Setup

At first of all you need to figure out the flow rate. Grab some watch and measure flow over one minute. You can use syringe to measure amount of water, or whatever you know volume or scale (remember 1g water =1ml water)
My pump got quite convenient flow rate which is ~5ml/minute.
If you have ready fertiliser (bought from a shop for example) and the rate didn't fit to one minutes, you might recalculate and mix fertiliser with demineralised water.
For example: you peristaltic pump got flow rate 7ml/min you want to add 5ml of fertiliser at once, and you have 200ml of the fertiliser, the math is:
7/5=X/200ml => X=7/5*200ml => X=280ml that's volume of the fertiliser mix. Now 280-200=80ml you have to mix 80ml of water with fertiliser, to get right amount of nutrients in one minute.
If you making your own fertiliser just simply recalculate you mixture, and add right amounts of powders to water. (but if you're enough experienced to make your own PMDD I don't need to explain anything)
Useful links:
Now timer, I've setup mine about 20 minutes before lights on, but depends on preferences. Again, on the internet you can find plenty of tutorials how and when dosing.
I've sicked the other end of the tube (outlet) to canister filter outlet just above the water surface so water is mixing instantly with the drops of fertiliser.
Final step is deaerating tube. Just run the pump for a while and see when liquid will reach the end of the tube, that's all.
Good luck.

Step 4: Thoughts

The electric motor (or gearbox need to figure out) is quite noisy, so I need to make sort of enclosure for pump itself. Quick-and-ugly solution might be a piece of foam.
It's good idea to separate micro and macro nutrients (two solutions, two pumps), but in my opinion for my 70L aquarium its overcomplicated. So I keep separate micro and macro and mix it together on weekly portions. Again google is your friend ;-).
The price for whole setup was 1/3 of the branded available in the shops, so in my opinion worth to try.
the white


kington99 (author)2013-10-22

thanks for this, I've been trying to work out how to get small enough doses using a peristaltic pump (I need approx. 2ml a week) and hadn't thought of the dilution tactic to get the total volume up. My only concern is that the fertiliser might separate out of the water over time, have you had any experience of this?

thewhite (author)kington992013-10-22

Hi. Never had any problems with separating, and I'd say is unlikely you'll have it. I don't know what type of fertiliser you're using, but it's usually a mixture of salts with water anyway. So adding water won;t do any harm.

kington99 (author)thewhite2013-10-22

That's a very good point, thanks for your help

fegundez1 (author)2009-10-17

nice setup, I see more people are realizing that the cannister filters sold for home water filtration (the ones that look like mini pool filters) work better and are cheaper than the massively priced ones that the pet shops sell. How do you make the fertalizer? I must have missed something here but its been a long night

thewhite (author)fegundez12009-10-17

Hi thanks for comment. Actually I have "massively-priced" canister filter Tetra EX600. The inline filter enclosure is only for heater and CO2 mixing. The fertiliser is made from acid salts Potassium Nitrate, Potassium Sulphate, Magnesium Sulphate, etc. see webpage<br />

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