It usually happens the same way. A week of storms, a pump timer that got knocked off, a vacation, and the pool goes from blue to cloudy to green in about four days. The first instinct is to drain it. Almost always, that's the wrong move: it's expensive, it can damage the shell in Miami's high water table, and it doesn't fix the reason the pool turned in the first place.
What works is a sequence. First, the pool gets brushed hard, walls and floor, to knock algae loose from the surface. Then it gets shocked with enough chlorine to actually kill the bloom, which is far more than a single bag. Then the pump runs continuously, with the filter cleaned or backwashed as it loads up with dead algae, sometimes twice a day for the first couple of days.
Over the next several days the water goes from green to grey to cloudy blue to clear. Each stage needs another test and another adjustment, especially pH, which shocking pushes around. A phosphate treatment at the end removes the food supply so the algae doesn't come straight back.
The shortcut people try is one dose of shock and a hope. It doesn't work because the chlorine is consumed before the algae is dead, and the pool is green again by the weekend. If your pool has turned, call us. A green pool recovery is a normal job for us, and it's much cheaper than a drain and refill.