Practical Steps in Cleaning a Liner Pond

  • Weather should be reasonably warm.  If fish are huddled at bottom of pond and still, they are hibernating, and must not be disturbed.  If they are swimming around and weather is reasonably warm outside it should be fine.
  • Make sure you have several hours and start early.  You may finish in a few hours, but for larger, dirtier ponds, I have taken up to 8 hours at the extreme.  An 8’x8′ pond with 2 men should be quite doable in 3-5 hours.  If you start early, you have a cushion.
  • For a good number of larger fish, prepare containment unit for Koi/Goldfish in unit that is ideally 3′ high and 4-5′ in diameter or other unit(s) that will accommodate comfortably.  Ensure stability of unit, and obtain netting that ideally connects tightly over unit.  Fish may jump out, otherwise, and it is best to monitor them closely during a clean out.
  • Add 15-25% pond water to unit depending on how dirty water is, to ensure fish are not shocked by new water.
  • Add a dechlorinator that also deals with chloramines incrementally with hose water! Leave a good bit of room at the top of containment unit.
  • Use an aerator to maintain oxygen level in containment unit.
  • Depending on depth of pond, you may drain some of pond water with a sump pump and accompanying hose prior to removing fish, in order to get to them.
  • Using net (there are sock type nets for larger fish that are quite helpful), gently guide fish into net and introduce into Stress coat conditioned containment unit.  Monitor for a few minutes to see that they are fine.
  • Turn off and disconnect pump.
  • Finish draining pond to garden beds/lawn/street/drain.
  • Remove all debris from pond such as tree and leaf related, etcetera.  I get on my hands and knees and pick debris out.  If some silt can be easily plucked out, then do so.
  • Power wash the rocks, being careful not to touch or abrade the liner.
  • Remove all filter media from waterfall/biofall and skimmer, if you have a skimmer with pump that circulates water back to waterfall, presumably.  Power wash media.  If mesh filter mats or other media have worn out, consider replacement.  Usually lava rocks and bio-balls are fine for years, but mesh mats wear out.
  • Reset loose rocks or lights, and replace light bulbs if applicable.
  • Prune plants as necessary.
  • Now you are ready to rinse.  (Recommend annual clean out).  Run 1-3 hoses into the pond and run the sump pump.  This method entails pumping a great deal of water to drain/lawn/beds/etc.  I have had years of success with this, but you will have to judge the practicality per your situation.  The purpose is simply to cycle the sludge out of the pond.  Once the water runs clear, you may go extreme by running hose over pond floor to see if mud still comes up, and continue rinsing, or just remove sump pump, reattach pond pump, reassemble filter and waterfall media and fill the pond.
  • As you fill the pond, and BEFORE returning fish to pond, add dechlorinator in layers to recommended dosage on bottle.  dechlorinator is crucial. Fish may well perish if this step is missed.
  • Remove netting from containment unit and gently return fish to pond.  Ease them in the water, guiding them from net with your free hand if possible/necessary.
  • Add beneficial bacteria.  It will restore bacteria to the pond that the clean out removed, so the pond does not turn green after clean out from absence of beneficial bacteria.  You may add the recommended dose by dispersing it in portions around the pond, especially the biofalls/waterfall.
  • Monitor the fish for awhile to ensure they are fine.
  • Boots/Waders
  • Containment Unit
  • Netting
  • Sump pump and 2-3″ hose for same
  • Power Washer (electric generally fine unless heavy algae buildup on rocks.  Gas?  be careful not to damage liner as powerful, and especially that no fuel/residue gets to pond-these tend to drip on occasion)
  • Dechlorinator (32oz or more, especially as you will be using for containment as well)
  • Beneficial bacteria
  • Gloves (optional)
  • Hats
  • Old nylon workout pants clean up better than jeans
  • Large net and maybe a sock net if concerned about big koi
Nycon Koi Sock Net
(Catch fish at front end and close back end with free hand.  Release into containment through safest end.
  • Aerator
  • pruners
  • replacement underwater light bulbs
  • Troubleshooting:
  • Cans of waterfall foam if any leak issues
  • Silicone if any sealant issues
  • If you would like a professional clean out, consult your local pond service professional.


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