Best Use for Pond Sludge?

My husband just cleaned out our koi pond and gave me about a metal trash can full of sludge -- mostly fish poop that has accumulated over the last year. I am wondering what the best use for this is. I know I could just throw it in the compost, but I'm also about to transplant my warm weather plants (tomatoes, peppers, cantaloupes) and I'm wondering whether this would be good stuff to just add to the bottom of the hole and plant on top of.

The other option would be to use it to create "compost tea." I don't have an active worm bin right now, and while I share a compost pile with my neighbor, it's not ready for action yet. So I was wondering if this fish poop sludge would be a good substitute for actual compost or worm castings in compost tea.

Thanks! :)


  • hmsadmin
    hmsadmin Posts: 123 admin

    Do you use any chemicals to control the pond chemistry? How's the salt content of the water?

    I would think, as long as there aren't chemical PH controls or other additives in the pond it came from, it would be great to use straight in the holes you dig for planting. The ammonia is likely high if you use it straight like this though, so maybe a layer of sludge, then an inch or two of soil layered on before you drop your plants in?

    Salt content may be something to consider depending on the chemistry of your water. This sludge may have a high concentration of salts and minerals built up as it precipitates out of the body of water over time. This is both awesome and not, depending on how high the concentrations are. I'm not sure of a test or anything you could do to check salt levels directly, but for this reason, it may be better to compost it so any salts and minerals are diluted before it comes in contact with your plants.

    The compost tea idea could be good too, but I have little experience and no advice I could give there haha!

    Good Luck and either way, keep us updated on what you do!

  • David The Good
    David The Good Posts: 2

    I would definitely use it in your beds. In F. H. King's "Farmers of Forty Centuries," he shares how Asian farmers would dredge the canals around their rice fields and put the sludge on the ground as fertilizer.

  • gardneto76
    gardneto76 Posts: 528 ✭✭✭✭

    Absolutely! I have an aquaponics system and I use the sludge after cleaning out my filter. I have drained sludge and water directly into the garden, Used it to make a compost tea (even adding weeds to my barrel), and just put the sludge in the dirt. I am currently letting a batch of sludge dry, as I don’t have a dire need for it, so I can mix it I with my dirt to plant in later.

  • Jens the Beekeeper
    Jens the Beekeeper Posts: 651 admin

    I can only second the other comments. Use it in your beds directly. From my opinion the tomatoes and peppers will benefit the most from this extra nutrient boost.

  • Merin Porter
    Merin Porter Posts: 1,026 admin

    Thanks, all! Direct into the beds it is! :)

  • cre8tiv369
    cre8tiv369 Posts: 67 ✭✭✭

    Depends on what you feed your koi... If you are feeding them pelletized feed, find out what is in it (does it contain any algaecides, poisons to control anything, medications for fish, does it come from a clean reliable source, etc). If you are feeding your koi bugs you raised yourself, then, there is no question it is good. Once you establish that info, test it. What is the PH, don't put alkaline on an acid loving plant and vice versa, but you still want to know the ph before you compost it as well (this is pond sludge, not organic matter and the ph can be drastic and may not compost as quickly if the ph is extreme). Most straight poop is not ready for roots, it needs to be composted first and then it becomes sweet smelling earthy compost vs shit and rotten stuff. Some poop is too hot and will kill plants if applied directly. So it is a good idea to just be safe and compost it (provided you think it's clean and doesn't have any bad stuff fed to the fish). Fish poop/sludge from a clean source of nature can be good, but composting it is better, let those microbes digest and transform poop into rich compost, sludge is dense and thick and lacks oxygen and needs to be blended with organic fiber to allow air and space for all those good bacteria to eat it and transform it. And then check the ph of the compost before you apply it to the soil (which of course you also checked the ph of the soil and it is perfect for those acid or alkaline or neutral loving plants.... right?). So.. bottom line, compost everything you can, cus composting fixes all the problems before you add them directly to your soil. Check and pay attention to PH (fast, easy, and cheap to test for ph at home). Be successful.

    -Peace, Love, and Hippie Thoughts-