First, you need to address why you have that problem to start with.
Which is a simple answer of that rooter is WAY too wet. You've created the perfect conditions for algae, rot, and damping off.
Take a fresh rooter and soak it in water for a few mins. Squeeze it out in your hand as hard as you can. Thats about how wet you want a rooter to stay, not much more. Ideally, you dont want anything that gets constant light to stay wet.
If you do a top feed in the early stages, you need to make sure its aimed properly so it doesnt hit the rooter and cause this.
Its better to do a single drip line and run it into the middle of the pot so it just wets the hydroton below the cube where the roots are.