Which coolant to buy when adding to an AIO

[NoxAstrum]

I have an Eiswolf 2 and I'm expanding my cooling loop to include my CPU. I want to continue using the existing fluid, but I'll need more to fill the new parts of the loop. Which coolant should I buy to ensure compatibility with the existing coolant in the Eiswolf 2? Are all alphacool coolants compatible with each other? If not, what product does the Eiswolf 2 come pre-filled with, Apex, ECO or Eiswasser?

 

[Eddy]

You can use Tec Protect or Apex liquid.