It occurs to me that with all the water supplies of the world going down the pipes, some areas are water guzzlers, yes? It is only fair that they be blocked from the water ahead of time with some sort of tedious method to restore their water after a while.
Hence this spell! This will turn water to dirty water, then to sludge, blocking the main water pipes of a whole area. Other uses could be to clog the engine of a tank, stopping the fuels from circulating and then stopping the tank from moving, of course. So, it has uses, yes?
To turn water to sludge, we need only focus on the impurities in the water, and 'make them enlarge.' This can be done with radiation, drawing from your own heat aura and then feeding he impurities. These need to be found by filtering the water from the biomass and bacteria, by making the water 'hot.' Then, 'the bacteria can be found' by 'going for density,' where the density of the water is separated from that of the bacteria and fungus by dividing cells, as, water does not really divide, does it? then it would be made into hydrogen and oxygen, of course.
So, to find the bacteria, we need to go for colours other than turquoise, water colours, and intensify density on that. This can be done by reversing charge on them, making them polarized with the water, bringing a wall together. This will make them charged for as long as you maintain charge, of course.
Or, you could collect all the fungal spores together, by, using magnetism to charge the sludge to collect and then after that leaving it to infest the area.