Automatic inline fert dosing

[Jimmy Dale]

Hi all, I have been dosing EI with a separate macro and trace and have been pretty happy with it. My only problem is that I am away occasionally and am sometimes a bit forgetful so an automatic fert dosing device would be good for me. I don't want anything in the tank which means that my dosing will have to take place in the cabinet. I am using an Eheim pro3 external filter and I think I have come up with an inline solution to automatic dosing:



What I have here is a peristaltic dosing pump with no return valves placed facing the appropriate direction and a 12 x 6 x 12 mm reducing tee. The peri pump will dose the ferts straight into the tee which will placed inline with the 12mm filter hose. A non return valve should keep the tank water from rushing back into the fertiliser bottle. I will connect the dosing pump to a seconds timer and calculate how long it takes to dose a given quantity and set the timer accordingly.

Has anyone tried this before?
Can anyone foresee any problems before I try this out?
Obviously I only have one pump so I will now need to switch to an all in one fertiliser like neutro+ is there anything I should take into consideration when switching ferts?

Cheers,
Jimmy

 

[DTL]

I'm not sure that the peristaltic will be able to overcome the back pressure from the main return.
I'd suggest a drip above the water line if your concerned about things in the tank.
E.g.

 

[Jimmy Dale]

I wondered if that might be the case. Either that the back pressure would be too much or it would work the other way and cause the ferts to rush in too quickly.

I'd suggest a drip above the water line if your concerned about things in the tank.

The reason I want to keep it out of the tank is more for aesthetics than anything else. What are you dosing yours with?

 

[Claire]

I too would worry about the backpressure on the pump as they aren't strong motors.
I have the line for mine (homemade all-in-one solution) dripping into the tank as DTL posted, but I just tuck the airline underneath the inflow pipe to hold it in place.

 

[DTL]

Ref your question "What are you dosing yours with?"
I use the pumps shown here:

DIY Ferts Auto Dose System | UK Aquatic Plant Society

 

[Jimmy Dale]

Thanks for your replies guys. Nice dosing system DTL.

 

[ian_m]

The peristaltic pump would overcome the pressure from the filter. Peristaltic pumps are rated to about 5 meter pump height and filters only about 1.5m.

However I would be seriously worried about the non return valves failing due to EI salts crystalizing in the valves thus allowing tank water past. You don't want your tank empting out via your EI container.

Much better to have an air gap and drip onto surface of water like has been previously mentioned. Doing it this way is much simpler, less connections to leak and less to go wrong. If you use a 4 wheel peristaltic pump you don't need valves as when pump is stationary liquid can't reverse flow past the pump. This means once the pipework is primed with liquid the liquid stays in the pipe, rather than require a valve to stop it running back into your EI container.

DIY dual peristaltic dosing pump with alternate switching. | UK Aquatic Plant Society

 

[Jimmy Dale]

Thanks for your responses all. Ian thanks for posting your build thread, that is a really nice share - good on ya! Following everyone's advice I will avoid dosing inline - although there is the appeal of keeping the pipes hidden away in the cabinet the risk of non return valve failure outweighs the benefits! I like the rimless style so aesthetics is important (although I vowed not to let them cause me to compromise function). I do have a spare stainless steel 6mm crook shaped tube which could be suitable for fert dosing straight into the tank. Once I have constructed it I will get a picture up. Cheers all!

 

[Nathaniel Whiteside]

Thanks for your responses all. Ian thanks for posting your build thread, that is a really nice share - good on ya! Following everyone's advice I will avoid dosing inline - although there is the appeal of keeping the pipes hidden away in the cabinet the risk of non return valve failure outweighs the benefits! I like the rimless style so aesthetics is important (although I vowed not to let them cause me to compromise function). I do have a spare stainless steel 6mm crook shaped tube which could be suitable for fert dosing straight into the tank. Once I have constructed it I will get a picture up. Cheers all!

Why not purchase a glass U bend?

Flo Reverto U Shape Small Glass CO2 Tube Connector

 

[Jimmy Dale]

Why not purchase a glass U bend?

I thought about this, if the fert solution was clear then this would be great but it's a muddy green / brown - this does not sit well with my glistening glassware paradise. The other possible problem is that one of those glass U bends would probably sit below the water line giving the opportunity for back-siphoning. although the stainless steel isn't exactly transparent, you won't see the build up of gunk inside it and I can cut it with a dremel to sit exactly where I want it above the water line.