Do I need a seal coat? What product do you recommend?

We recommend seal coating any surfaces that will be submerged in FlowCast. Seal coats help prevent air and moisture from migrating out of submerged materials, which can cause bubbles. UVPoxy is the preferred system for seal coats as it is a faster curing resin made for applying in thin layers. Cured seal coats should be abraded and cleaned before proceeding with pours.