I got a 2 inch trash pump with the goal of vacuuming the muck. On Amazon Prime it was about two hundred dollars, free delivery. Pump passing through solids up to three quarter inch max. We made a vacuum head to block gravel right at a half inch (I have lots of gravel for fish beds) Once you establish a solid flow (up to 120 gallons per minute), where any air in-leakage at the intake is totally defeating, you can go for nasty black muck and sunk leaves. It's a lot of water and nasty, needing a good place to go..

Dan McWhirter
DannyMac