Most fall pond advice is a list of ten things with no order and no timing. That is the part people actually get wrong. Netting put up too late is useless. Bacteria added too early is wasted money. Feeding fish one week too long is the single most common cause of a dead koi in February.
Fall pond work is driven by water temperature, not the calendar. Buy a cheap floating pond thermometer, read it at the same time each day, and work off that. In the Philadelphia area the sequence below typically runs from late September through mid November, but a warm October can push it two weeks either way.
The short version
| Water temp | What to do |
|---|---|
| Above 60F | Normal feeding. Get netting ready. |
| 60 to 55F | Net goes on. Switch to wheat germ or cold water food. |
| 55 to 50F | Trim plants. Pull sunken leaves. Start cold water bacteria. |
| At 50F | Stop feeding entirely. Move hardy lilies deep. |
| Below 45F | Decide: shut down or run through winter. |
Above 60 degrees: get set up
Nothing urgent yet, but this is when the work is easy and cheap.
Buy your netting now, before the garden centers sell out, and measure the pond so you are not guessing. Clear out any dead or yellowing plant material you can already see. Check your skimmer basket and clean the pump intake while the water is still comfortable to reach into.
If anything on the system has been limping all summer, a noisy pump, a leaking fitting, a UV bulb past its hours, fix it now. Pulling a pump in 45 degree water is a genuinely unpleasant job.
60 to 55 degrees: netting and a food change
Netting goes on before the leaves fall, not after. This is the single highest-value thing on the list. A net that goes up on time turns the entire fall cleanup into rolling up a tarp. A net that goes up after the first big drop just traps the leaves you already needed to remove.
Tent the net slightly above the water rather than letting it sag onto the surface. A sagging net collects leaves in the water, which defeats the point, and it can trap a fish that comes up to the surface. Stake or weight the edges so wind does not lift it.
At the same time, switch to a wheat germ or cold water fish food. Below about 60 degrees a koi's digestion slows down and protein-heavy summer food starts passing through only partly digested, which fouls the water and stresses the fish. Wheat germ is easier to process at low temperatures.
55 to 50 degrees: plants and debris
Trim hardy marginal plants back to roughly 2 inches above the water line. Cattails, iris, rushes, pickerel. Dead foliage left standing will flop into the water over the winter and rot there.
Trim waterlily leaves and stems to 2 or 3 inches above the base of the plant. The leaves are going to die back regardless, and you would much rather they decompose in your yard waste than in the pond.
Scoop out the leaves that are already on the bottom. Use a long handled pond net and work in sections. You are not trying to get every last leaf. You are trying to remove the bulk of it before it breaks down. Decaying organic matter on the bottom is where the real winter problem starts: as it breaks down it consumes oxygen and releases gases, and under a sealed layer of ice those gases have nowhere to go.
Check the skimmer basket again. In leaf season it can fill in a day.
Start cold water beneficial bacteria once you are reliably under 55. Standard warm water bacteria colonies go dormant in the cold, so the cold water formulation uses strains that stay active. Twice weekly for the first two weeks, then once a week until the surface starts to freeze.
At 50 degrees: stop feeding
This is the one that matters most and the one people second-guess.
Once the water is consistently at or below 50 degrees, stop feeding your fish entirely. Not less food. No food.
Below 50 a koi's metabolism slows to the point where it cannot reliably digest what it eats. Food sitting undigested in the gut is a genuine way to lose a fish over the winter. The fish is not starving. It is doing exactly what it evolved to do, dropping into a near-dormant state and living off reserves until spring.
They will still come to the surface and look at you expectantly. Ignore them. This is normal, and it is the single most common mistake we see.
Watch for a few warm days in November that push the water back over 50. Unless it stays there for several days, do not resume feeding. The fish are better served by a consistent fast than by a false start.
Hardy waterlilies go deep now. Drop the pot into the deepest part of the pond so the crown sits below the ice line. Do not bring them inside. They need a cold dormant period and they will be fine under the ice.
Tropical waterlilies are the opposite. Bring them in if you want to keep them. Hold the pot in water around 50 degrees, or lift the tuber and store it in damp sand somewhere cool and dark. Be realistic about this one: even experienced growers lose a good share of tropicals in storage. Many pond owners treat them as annuals and replace them in spring, and that is a defensible choice rather than a failure.
Stop fertilizing everything after the first frost.
Below 45 degrees: pick your winter plan
At this point fall is over and you are making a winter decision. Shut the system down and drain the plumbing, or run it through the season. Both are legitimate. Which one is right depends on how your pond is built, how deep it is, and whether you want to look at moving water in January.
That decision, including how to keep a hole open in the ice and what depth you actually need, is covered in detail in our winter pond care guide.
What you can skip
A few things show up on fall checklists that are not worth your time:
- Draining the pond for the winter. Almost never correct. An empty liner is more vulnerable to damage than a full one, and your fish need the water.
- A full cleanout in fall. Spring is the right time for that. A fall cleanout strips the beneficial bacteria right when the pond is heading into a stressful period.
- Removing every single leaf. Diminishing returns fast. Get the bulk of it.
- Breaking the ice with anything. Not a fall issue, but worth saying early: the concussion can injure or kill fish. There is a correct way to open a hole, and hitting it is not it.
When it is worth calling someone
If the pond is large, if it is deep enough that scooping the bottom means getting in it, or if the equipment needs to come out and you are not sure what reconnects where in spring, this is a reasonable thing to hand off. We also tend to find problems during a fall visit, a liner seam starting to separate, a failing check valve, that are far cheaper to fix in October than in April.
Our fall shutdown service covers the whole sequence including the equipment, and there is a breakdown of what it involves, when to book it and what it runs in our fall pond shutdown guide.
Get on the fall schedule
Fall booking fills from roughly the first week of October through the end of November, and the last two weeks go fastest because that is when everybody notices the leaves at once. If you want it done before the water drops, earlier is better.
Get in touch and we will tell you honestly whether your pond needs us or whether it is a weekend of your own time. We serve Philadelphia, Bucks, Montgomery, Delaware and Chester counties, and South Jersey.