The swamp

First, vacuum the crap off the bottom but rig your filter so you’re pumping it straight out to waste; you don’t want all that sludge going through your sand or DE (that’d be a great way to ruin your new filter). Then broacast aluminium sulfate and leave it say, 36 hours. That should clear the water a bit but you’ll have another layer of sludge on the bottom. Vacuum that to waste too. If you can’t see the bottom, repeat the alum treatment. If you can see the bottom, do a shock treatment with chlorine; you’re trying to get levels up to 16 ppm. (If you don’t want to buy the expensive powder at this point, get some generic supermarket bleach whose active (and only) ingredient is sodium hypochlorite.) Start up your filter and let it run for a day or so. Water should be clearing up but may still be milky. If so, another alum treatment (filter still running) and leave overnight. Vac again and backwash. Things should be clearing up by now. Keep your chlorine up for a few days and apply more alum (vac & backwash) if things are still a little cloudy. Also, before you think of swimming in it, throw in a generous dose of Sodium Bicarbonate to buffer your pH and get your alkalinity up.

That’ll be $85, thank you.