[Woodstock]

I emailed Ralf Prehn to ask about dosing pumps. You can view his site here: cashh.de

Here is his response to my question asking about the LiterMeter III, the Aquamedic, and the GroTech TECH III dosing pumps.

Hi Doni Marie,
thank you very much for your kind words.

Please stay away from the Aquamedic ones, I've had one and threw it away.
The working principle of all those pumps is, that the hose inside the pump is squeezed with some small, rotating wheels. That moves the liquid.
The Aquamedic ones have only 2 wheels and not 3 like the more expensive ones.
This makes, that it is possible, that the wheels stop in a position, that does not close the hose fully, so liquid will poor back and there is no dosing accuracy, or water may flow out of the tank. Aquamedic ships a one-way valve with the pump to prevent this, but these valves are not chemical proof :-(.
They really should have designed the pumps more carefully.

The Grotech one (TECH III), maybe with extention module, if u need more than 3 pumps, seems the right one to me. Its relatively easy to programm (simply enter the volume) and very reliable. It does not use the one way valves, because it does not have to ;-).

I use it only for my trace elements and not for balling, because I need more than the maximum of 1.9 liters a day, that a Grotech channel supports as max.
volume.

Unfortunately I don't know the LiterMeter III personally.
You might give it a chance, if it has at lease 3 of the mentioned wheels and no one-way valves.

Hopefully I could make myself understand, English is (as you already guessed ;-) not my native language.
Best,
Ralf