Greeny blue mold on Pharg mem. Dick Clements roots

[Susie11]

I have had my new mem. Dick Clements for a week and I have just found some fluffy white fungus or mold growing on the top of the rockwool cubes. Also, I have seen that there is a blue / green spotty mold growing on the roots at the bottom of the pot .

I have a bottle of hydrogen peroxide at 3% and I am wondering how I go about using it. I have read that after application it is wise to let the roots dry off but what with this being a phrag is this the right way to go about it?

I will post some pics tomorrow and I intend to repot tomorrow but which medium should I choose? I have a rockwool and perlite mix or I could use straight up sphag. I favour the sphag as it has antiseptic qualities but then the rockwool is more familiar to me.

I welcome your guidance.