Fertiliser dosing setup

[Dan Earl A]

I have a Kamoer X1 dosing pump which I use to dose APT3. I'm looking for a neat solution for injecting the fertiliser from the outlet pipe of the pump into the aquarium, suitable for a single inlet. Currently I'm using a glass u-bend (for CO2 injection) over the rim of the tank but I'd like to tidy this up and even have the fertiliser inject below the water surface. Has anyone come up with a neat solution I could adopt? Thanks all!

 

[tam]

I'm interested in this too. I was looking at the ubends, good to know the glass ones fit over the tubing. You can get acrylic ubends which seem longer.
Most dosing fittings seem designed for multiple heads rather than one though.

 

[hypnogogia]

There’s a risk that if it enters the water under the water line you set up a syphon and have backflow into your fertiliser reservoir. Not a safe way to do it.

I have come across some people injecting straight into the filter return pipe using the Venturi principle.

 

[Dan Earl A]

There’s a risk that if it enters the water under the water line you set up a syphon and have backflow into your fertiliser reservoir. Not a safe way to do it

This was my concern so I've set up a temporary arrange in the tank to monitor if this does occur. The APT has quite a visible yellow colouration so I'm hoping I can detect any syphoning. I also have a non return valve to prevent movement of water back to the pump.

 

[Dan Earl A]

I have come across some people injecting straight into the filter return pipe using the Venturi principle.

What does this look like? How are they connecting the pump outlet to the return pipe? I'd be interested in understanding what sounds like a quite minimalist approach. Thanks

 

[Dan Earl A]

I'm interested in this too. I was looking at the ubends, good to know the glass ones fit over the tubing. You can get acrylic ubends which seem longer.
Most dosing fittings seem designed for multiple heads rather than one though.

Yes, agree. Chihiros have what seams to be a neat solution but it's for multiple outlets which I simply don't need.

 

[hypnogogia]

What does this look like? How are they connecting the pump outlet to the return pipe? I'd be interested in understanding what sounds like a quite minimalist approach. Thanks

Chads Arduino Build

www.plantedtank.net

 

[Dan Earl A]

Chads Arduino Build

www.plantedtank.net

This is super complex!

 

[hypnogogia]

This is super complex!

Not really. All you need is one of these:

3/4" Irrigation Venturi Fertilizer Mixer Injectors Agriculture Water Tube-u- | eBay

A venturi is a device which creates a vacuum when fluid flows through it. The fluid which creates the vacuum is know as the motive fluid. The motive fluid for irrigation injectors is the irrigation water itself.

www.ebay.co.uk

 

[simon_the_plant_nerd]

This is super complex!

Agreed. But the bit that’s relevant starts a long way down the thread on post #61. The rest of it is about a DIY aquarium computer.

Chads Arduino Build

www.plantedtank.net

 

[Dan Earl A]

Not really. All you need is one of these

Okay thanks, that's helpful. How is this set up in an aquarium - isn't it a 'constantly on' attachment which will want to draw the APT through the pump/outlet pipe and from the reservoir? How is it connected to the pump outlet? Apologies if these are dumb questions but it seems in principle a good concept but I'm not clear how to make it a reality in my situation.

 

[simon_the_plant_nerd]

isn't it a 'constantly on' attachment which will want to draw the APT through the pump/outlet pipe and from the reservoir?

Essentially, yes. The Venturi effect is when the fluid pressure drops as the velocity of the fluid increases as it passes through a constriction. The relationship between fluid pressure and velocity is a fundamental law of fluid dynamics. As the pressure drops in the constriction, the negative pressure can be used in an engineering process to draw another fluid into the system. This is how fertiliser can be pulled into an irrigation system, or air into a protein skimmer for example. While the fluid is flowing through the constriction, there will always be a pressure drop.

How is it connected to the pump outlet?

A peristaltic dosing pump uses peristalsis to move a fluid from one place to another. When the pump head rotates, it uses rollers to compress and re-expand the tube in which the fluid flows. As it rotates it forms a wave like motion pulling fluid into the tube and pushing it out of the opposite end. When the pump is at rest, the tube is compressed by a roller, essentially acting as a valve. This prevents fluid moving within the tube.

If you suck up a straw of juice then put your finger on the top, you’ll notice that the juice doesn’t come out of the bottom. This is the atmospheric pressure acting on the open end. You can then suck on the end of the straw and you’ll find the juice still doesn’t come out. You’re creating negative pressure with your mouth but because your finger is preventing the pressure from equalising, it doesn’t move. Once you release your finger, the pressure equalises and you get a tasty drink of juice.

Now think of the tube from your dosing pump as the straw, the fertiliser is your juice and the pump head is your finger. The negative pressure created by the Venturi effect is your mouth. While the pump head is at rest, no fertiliser flows into the system. Once the pump head moves however, re-expanding the tube, the pressure in the tube equalises and the Venturi effect pulls fertiliser into the system.

EDIT: Just an addition, the peristaltic head isn’t actually required in a set up like this now and the negative pressure in the Venturi will draw fluid into the system without the ‘pumping’ assistance of the pump. The head is acting as a valve. You could achieve the same thing with a solenoid, timer and check valve if you wanted. The check valve would prevent fluid going the ‘wrong way’ should flow in your main pipe stop and the pressures equalise.

 

[LMuhlen]

I don't see a reason to have a venturi to inject into the filter outlet line. The autodoser should have enough pressure and the venturi doesn't prevent tank water from draining out to the fertilizer reservoir. If the filter turns off for whatever reason, the pressure in the venturi goes back to normal and you are prone to having an issue if the autodoser and the check valve both fail to hold the flow in the wrong direction. If you want to dose straight into the filter hose, just go for it. It can be done as simply as drilling a hole on the tube and gluing the autodoser outflow pipe into it, or you could use something like a CO2 inline diffuser without the ceramic for a more professional look.

 

[simon_the_plant_nerd]

I don't see a reason to have a venturi to inject into the filter outlet line. The autodoser should have enough pressure and the venturi doesn't prevent tank water from draining out to the fertilizer reservoir. If the filter turns off for whatever reason, the pressure in the venturi goes back to normal and you are prone to having an issue if the autodoser and the check valve both fail to hold the flow in the wrong direction. If you want to dose straight into the filter hose, just go for it. It can be done as simply as drilling a hole on the tube and gluing the autodoser outflow pipe into it, or you could use something like a CO2 inline diffuser without the ceramic for a more professional look.

Well yes, but you describe the same thing without the benefit of negative pressure drawing fluid into the system under normal operation. Also ‘drilling a hole and gluing’ sounds a little easier to get wrong for someone.

I personally have an open ended pipe above water level. Sometimes the simplest solution is the best?

 

[Dan Earl A]

I personally have an open ended pipe above water level. Sometimes the simplest solution is the best?

This was my starting point and I guess it's my end point too! Thanks for the science trip though, today I learnt something!