Fall Koi Pond Care Tips

By now, you should be feeling the cool, fall weather of the Central Valley. The koi in the pond are likely noticing the weather change, as well. Below are some Fall pond care suggestions to help guide you and your koi pond friends into the upcoming colder months.

Remove Falling Leaves

Keep the koi pond clear of falling leaves and tree debris. This can be done by skimming the top of the pond as well as removing decaying leaves from the bottom of the pond. Empty skimmer baskets and leaf baskets frequently or when they begin to fill up with leaves/twigs.

It is important to remove the leaves and branches that have fallen into your pond because they can harm the koi and your pond system. Leaves and smaller twigs can get into your mechanical filter and can cause damage.

Another problem with falling leaves and debris that are left to sink to the bottom of the pond will begin to decay and eventually impact your water quality. Over a long period of time, sunken leaves and debris accumulate and form sludge at the bottom of the pond. This sludge will create a water quality problem and most likely lead to cloudy water, the more the koi swim around in it, the more it will get stirred up.

If the leaves and debris are left to accumulate, you will likely have an algae bloom in spring. The bad bacteria begin to attack the leaves, releasing harmful gases known as, “Hydrogen Sulfide” acid that smells like rotten eggs and is deadly to both koi and humans. So, addressing the leaves early will prevent this problematic issue.

Photo of decaying leaves in a pond that may sink to the bottom and begin the process of creating sludge if not removed quickly.

Koi Feeding in Colder Water Temperatures

In fall, our outside temperatures have dropped significantly, which means the pond’s water temperature has also dropped. Please measure the water temperature by utilizing a pond/pool thermometer to keep track of the changing water temperature.

When the water temperatures start to drop, it is time to switch from a high-protein koi food to a lower-protein koi food that is less than 35% protein, and higher in carbohydrates, i.e. wheat germ.

There are koi food manufacturers who market products as winter or cold-water food but always read the nutritional label to ensure the protein is less than 35% to be safe. The reason for this is that as the water temperatures decrease so will the metabolism of the koi. You will notice the koi are not as active as before. Some mornings the koi may even be sitting at the bottom of the pond, which is a sign they are entering hibernation and do not require as much food as before, if any at all.

Also, as you switch the koi food to a lower protein diet, make sure you also adjust your feeding schedule. If using an automatic koi feeder, either remove it or reduce the feeding times and amounts. If feeding by hand, consider feeding once or twice a day.

Feeding koi carb-heavy, low-protein koi food makes it easier to digest compared to the heavy protein growth food. Not feeding the koi during cold water temperatures will allow them to live off their fat reserves, as well as they will graze on the algae found growing on the pond walls.

Please follow the recommended temperature/feeding schedule in this article. It is not recommended to feed the koi when the water temperature drops to 40F or lower. 

Assessing Pond Equipment

Fall is a great time to check your current pond configuration and assess whether you need any repairs or upgrades. These types of repairs or upgrades are best done in the cooler weather of fall/winter when the koi are hibernating and not eating to minimize the effect on the koi.

Some types of common repairs are:

  • Checking for leaks – Is water evaporating out of the pond too fast?
  • Inspecting all hoses/valves.
  • Assessing waterfall flow and general pond circulation.
  • Adding and/or removing plants in or around the pond.

It is important to check your filtration vs. pond stock. Are you overstocked with koi? Can your filter keep up?

Balancing your filtration system to the number of koi is far better than adding a chemical cocktail into the pond. There is NEVER a need to go and dump some type of chemical to ward off any parasite of future koi problem. With colder water temperatures, remember the koi’s metabolism is slow and so is their immune system. Harsh chemicals on weakened koi are only a recipe for disaster. If you are having a koi health issue, please seek out the advice of an experienced koi hobbyist in the club, before adding any chemicals to your koi pond.