The current advice I have received from EK is to use corrosion inhibitors containing ethylene glycol.
This is for an EK Supreme HF block Full Nickel.

I profess I am not great expert on water cooling but and enthusiast enjoying the hobby. I am currently sitting on the unopened block and to be fir cannot say I see any external problems.
I am also to understand opening the block invalidates the warranty.

What is frustrating is not knowing what to do. The community response is enough that I am not confident on using the block in my loop for fear the issue develops (a problem I can ill afford). I am also unhappy using Anti freeze in the loop due to its poisonous nature and having a young daughter in the house.

Has anyone got any advice for those of us holding relatively (4 months old) new blocks and unsure what to do with them?

For reference I already have bought and received 5ltrs of Mayhems Ultra Pure H20 and have a kill coil on order.