Osmosis, popularly known as Fibreglass Cancer or blisters, is one of the worst issues with fibreglass pools.


When contaminated water from the outside of the pool (soil area) filters to inside the fibreglass and penetrates into the top-coat, it shows as blisters or bumps on the pool’s surface. These blisters can vary in size from +3mm to the size of a fist. Once they reach their limit, these blisters will eventually crack, leaving behind small black/brown marks on the pool surface, bringing bacteria and nasty pollution to the water. Due to the high mineral content in these cracks, algae formation takes place which is called black plague.

Once osmosis breaks out in your pool, the water conditions are less than recommended for your family, particularly to your little ones.


Plus, it is not easy to get rid of these black spots without having to professionally resurface the pool with a new layer of fibreglass correctly installed.



Osmosis is the guest you would never want to take a dip in your pool with, but understanding what you’re up against can help you find the right fix. If you detect black spots in your pool, immediately contact us to help you with your fibreglass resurfacing pool service to bring your pool back to good health in the most affordable manner.