You’ve worked so hard to shovel/suck/excavate bucketsful of goopy sludge from your fish pond and now you’re staring at it blankly and wondering what to do with all that muck? Fortunately, pond scum, fish poop, decaying organic matter and algae are mega-rich in nutrients, including potassium and phosphorus. This, combined with high-levels of nitrogen, makes them talented composters and, where the act of decaying inside your pond can cause significant problems including fish loss, this makes for the ideal food for terrestrial plants. As long as your pond isn’t having any trouble that has required use of chemicals or salt, all those living microbes that you’ve scraped off the top and bottom are perfectly suited as a fertilizer. You can directly apply the sludge to the garden beds by the trowel-full, and if there are any offensive odors, you can bury the sludge underneath a few inches of soil. This is powerful stuff - a quart or two poured around the base of a benignly neglected tree can double its growth rate in the next season. Compost tea is also an option that will provide a solid but not so overwhelming boost.
If you’re spring cleaning, this is an ideal time to add the sludge to your compost pile and supercharge the nutrients. Start with a good 4-6 inch layer of brown materials like last year’s leaves or shredded cardboard. Mix your pond sludge with some other green materials like coffee grounds, vegetable scraps and yard clippings, then spread it in a 3-4 inch layer over the brown stuff in your bin. Add some garden soil, moisten it with water, then repeat until your pile is about 3 feet high. Turn it every few days until it’s dark brown with a crumbly texture and rich, earthy aroma and use it to amend your soil wherever needed. You can even mix the compost with perlite to make a wonderful indoor potting soil.
