[Boli]

copper sulphate pentahydate?

Is this copper suphate solution that you use in chemistry to grow crystals, if so when it starts to evaporate cystals will most likely start to form possibly becoming a hazard to cascade cups for example.

on the up side though it is poisonous and nothing will grown in it so you'll see a nice clear blue all year round without cause to add additives .

Change the molarity of the solution (1/4 water maybe) to decrease its viscosity and maybe it will be more usable and still retains a higher thermal conductivity than water.

I think the biggest problem you'll have to overcome though is crystal formation. that and ANY currant that passes thorough it will cause problems through corrosion, and your block will just become slowly eaten away... though if you ever want to copper plate something you can just dip it into your res on a wire attached to a battery, and the other end touching your waterblock