1. That is an Aluminium radiator and EK don't recommend using their products with it. Most people stay right away from Aluminium these days because it can cause big problems with corrosion when it is combined in a loop with other metals.
I agree about mixing metals, but I didn't find lots of passive radiators that are not made of aluminium :/
2. There is no such thing as g1/4 tubing. g1/4 is the size of the threaded part on fittings and components. Tubing sizes commonly used these days are 3/8, 7/16 and 1/2 ... you will need fittings and tubing that match each other.
I mixed the units, I updated the first post. The tubing is 3/8 and I bought G1/4 couplings.
3. If you are not using fans I don't really see the point of the expensive Aquaero ... its a fan controller. If you just want to control a DDC pump you can get a PWM controlled model. You can also get the USB flow meter that doesn't require the Aquaero either.
The major issue I have, is that my motherboard doesn't have any auto shutdown options. If a fan stops spinning or a component gets to hot, I have nothing to cut the power.
By a fan stopping spinning, it could be the RPM signal from the flowmeter like : Koolance INS-FM17N+ADT-FM03
The flow sensor seems to be one originally designed for much narrower tubing than what is used these days but as long as you set its calibration correctly it has no maximum flow rate. Sven was exactly right about the flow rate of the pump ... It will pump 400LPH into open air but even the smallest restriction like tubing or a radiator will drop the flow rate way, way down.
I checked Digmesa's website, the flowsensor can measure a flow between 10LPH and 486 LPH. So it should be fine.