I don't know what size tank you have, how bad it is, or what livestock. But years ago after a tank disaster I walked away from my tank for almost a year. I shut off the lights and ancillary equipment and let just the return pump and heater run. There were still some fish in the tank, but I just ignored everything. The tank got morning sun and it wasn't long before you couldn't see in the tank.
After 9-10 months I got diagnosed with Kidney Cancer (Fully recovered and clean now 13 years later). I didn't want to deal with recooperating without my tank.
So I turned on the lights and here was a tank (400g) packed with rock just covered with a shag algae. There was over 1000lbs of rock in the tank, and rock mounted on the back wall. Removing it to clean wasn't an option. So I drained the tank to a few inches of water, enough for the fish to swim in. And then got out the pressure washer and blew off all the rocks. And siphoned and netted out all the crap, filled the tank with fresh salt water, added some carbon, and a few days later started packing the tank with life - And the tank took off and thrived.
Dave B