Hello, this is our first year as an above ground pool owner. We live in London and went on holiday for 9 days. Came back and the pool was green. We left it at the right levels, with a chlorine dispenser. Cover partially on. It rained a lot. Now I’ve tried to rebalance the chorine, put algaeside in, brushed it off the edges, ran the filter. But no change. Any ideas of how we can fix this before the next heat wave? Thanks.