How to remove hard water scale from a fiberglass fountain?

Run a gallon of white vinegar through the fountain overnight, with no pets or toddlers around. Pour several cups over the Buddha. The next day, clean the Buddha with a small amount of toothpaste and soft toothbrush. Rinse the Buddha with the fountain water. Within a day, the water, Buddha, and other plexiglass should be sparkling.

The Works from Walmart is the only thing that works for me. Cheap too! Test a small area first though because it's very strong and may damage paint.

Have you tried a little white vinegar? It will dissolve the minerals. I assume the water is recycled. This should help

vinegar. pour it on, leave it for a little while, scrub it off w/ an old scrubber sponge from the kitchen sink. OR use CLR, from the hardware store. ask if its safe for the fiberglass, though.

This might help you: https://www.hunker.com/13424138/how-to-remove-mineral-stains-from-a-fountain

Vinegar or CLR should handle that easily.