Make your white PVC purple coralline

[SmartWrasse]

If you want to put some quick color on the white PVC plastic showing inside your tank, paint it with purple PVC primer. You can slop it on and put thick vs thin for a pattern effect. It just needs to dry well & cure before it is placed in the tank :mixed:

[Atticus]

I would also suggest roughing the surface of the pcv with steel wool or sand paper to help coraline stick to it's surface.