We have had an aquarium for years - tropical fresh water fish. Last week there was quite a build-up of algae on the glass and on the gravel so I cleaned it up with the usual scrub brush. Yesterday we had 6 dead fish and today another 2. These are the first losses for more than a year. The water is now really cloudy and looks very unhealthy. We have not introduced any new fish or plants and are still using the same fish food.
Could I have disturbed the natural balance of the tank somehow by my cleaning? I have done this in the past a few times but never with this catastrophic effect. Appreciate any advice thanks.