When to Start Feeding Koi After Winter? Guide to Best Spring Feeding Practices
As temperatures rise and the winter season starts to shift into spring, a garden ponds eco-system slowly start to become active again. Over the winter most pond koi will be in a peaceful hibernative state (technically, “torpor“) under the frozen ice, and won’t have an interest (or need) for food until water temperatures increase. As explained in our dedicated koi winter care guide, carp begin to slow down when water temperatures hit around 50ºF (10°c), and they’ll remain in this low-energy state until water temperatures rise above this point.
During this period a kois bodily functions slow down to a crawl, including their metabolisms and immune system. Their metabolisms govern their natural feeding instincts, and as this function is all but switched off, no food is necessary until it switches on again in warmer conditions.
Adding food over winter won’t end up rotting in a fishes gut (a common myth), but it will end up rotting on the pond floor and contribute to waste and ammonia build-up. Koi carp won’t just eat for the sake of eating, and if they don’t need food, it’ll simply be left to decay in the pond. This is the primary reason we don’t feed koi over winter, as both the fish and the pond is in a more vulnerable state and extra waste from food simply puts more stress on a sleepy eco-system.
Similar to winter feeding, you can determine when to start feeding koi again in spring based on water temperature, but we personally prefer to base our feeding routine on a koi’s behaviour, as well. Monitoring water temperature is a good part of fish keeping, but so is learning to read your koi – so why not do both?
When should you begin feeding your koi again?
Sadly, there is no hard-and-fast rule to determine when you koi are ready for their after-winter grub, but you can certainly make some educated guesses based on both temperature, water quality, and fish behaviour.
Method 1: Reading Water Temperature:
Firstly, if you like to cover all bases and enjoy the more technical aspects of fish keeping, having a pond thermometer is always handy throughout the year as it goes hand-in-hand with certain aspects of water quality. In colder weather it’s useful for determining when to start or stop fish feeding, and in summer it’s useful when testing water quality as it’s directly related to ammonia potency (alongside pH). Basically, it’s a good tool to have, and when temperatures reach above 50ºF (10°c), fish will slowly start to come out of torpor. If you’re just going by temperature alone, we personally find from experience that koi will start eating again within the 55ºF (13°c) to 60ºF (16°c) temperature range. It depends on your fish, as some will eat earlier than others, but this is a reasonable estimate to go by if behaviour also checks out (see below).
Method 2: Reading Fish Behaviour:
If your water thermometer is reading increasing temperatures, or even if you don’t have a thermometer, the next step would be to observe the daily behaviour of your fish. As koi begin to come out of their hibernative state, their bodily functions, including metabolism, start to fire-up once more. With this increase in bodily activity comes a return of their natural instincts to search for food, which will be presented in their behaviour. When your koi start to become hungry they’ll begin slowly swimming around the pond searching for food. If they’re used to you hand feeding them, they’ll gradually come to greet you at the surface as temperatures increase. At this point, it’s safe to start feeding very small amounts and monitoring wastage. If your koi are actively eating all food, you can slowly increase the amount every day until there is a little waste. If there is pellets left floating on water, you should instead decrease the amount until all daily food is being eaten.
Don’t be afraid to try feeding!
Food will NOT rot in a koi’s body, but instead will simply contribute to waste on the pond floor. This is why monitoring feed at the start of the year is important, as the eco-system (including beneficial bacteria) are still in maintenance-mode and even small drops in water quality can cause stress on fish. If your fish are taking food, it means they’re telling you to prepare more grub in future! If there is pellets left behind, just scoop them out with a pond net and adjust feeding accordingly until your koi properly wake up.
Will feeding too early make my koi sick? (the rotting myth)
As touched upon in similar articles, there is a common misconception that food you provide your koi over winter will end up rotting inside their gut until spring. Sadly, this train of thought has become quite widespread, and may delay newer fish keepers feeding their koi after winter, even when conditions are right.
The idea that food rots inside fish over winter is just plain wrong, and there is no scientific evidence to suggest this happens in any species of fish, including carp. When koi are hibernating their metabolism is almost shut-off, and this governs their instincts to feed. With such low bodily functions comes equally low energy requirements, and with that, a lack of interest in food. A hibernating koi won’t eat for the sake of it, and if they do happen to eat (maybe a day is warmer than usual), it will just be slowly processed as normal and excreted as waste. Even though a fishes bodily functions have slowed, it doesn’t mean they’re not working altogether. Beneficial bacteria living inside a carps gut will still be able to slowly break down food which passes through it, and it won’t just be left there to rot over the winter season. In other words, don’t be afraid to test some feed as warmer weather hits!
What koi food is best for Spring feeding?
Many koi keepers choose to feed their fish with a plant based protein feed, such as wheatgerm, in colder weather due to it’s potential beneficial properties. Wheatgerm foods are said to be more easily digestible and will release energy at a more gradual pace, which sounds like a good choice for colder weather feeding. With that said, we’re not totally convinced on these statements, and instead prefer to choose wheatgerm based on it’s great healthy fat profile and wide vitamin complex – two things that are important for a healthy hibernation (torpor) period.
It should also be noted that contrary to what some manufacturers may claim, you can still safely feed koi summer feeds (high aquatic protein) in colder weather without concern. The problem with feeds which are super high in nutrients is that if they are left uneaten they will cause faster drops in water quality compared to plant based feeds. Taking this into account, so long as feeding is monitored and any waste pellets removed, either feed type is fine so long as it’s being eaten!
As a koi keeper, I personally use a high quality summer feed year-round while closely monitoring feeding to prevent wastage. My fish are quite fussy in general, and although I have tried wheatgerm feeds, they just don’t seem to like them as much! Even so, wheatgerm can still be beneficial due to it’s high fat profile which helps koi pack on extra weight before and after winter in preparation for the upcoming seasonal change. If you want to try wheatgerm, we recommend mixing it in with a small amount of a summer feed for the best of both worlds for late-winter/early-spring feeding. You can then switch to a full summer feed routine as your koi become much more active towards the end of spring!
Not sure what feeds are the best? Check our dedicated articles below that list our personal recommendations:
Don’t forget the rest of Spring Maintenance!
Knowing when to start feeding your koi is an important step to ensure they have the best start to the year, but there are other aspects of spring maintenance that should also be considered.
Before feeding fish, you need to make sure your water quality is in good standing, otherwise you’ll just be adding more waste (and ammonia) to the system. If you have a good winter routine in place, your spring routine won’t be too involved, as not much happens in cold weather as ponds slow down to a crawl. However, if you haven’t performed a good clean up in winter, you’ll want to do that in early spring to ensure your water quality remains good and feeding can be increased. Any bottom muck, especially black muck, should be removed and filter media should be inspected and cleaned. Afterwards, pumps can be turned back-on and the pond supplemented with beneficial bacteria to really kick-start the eco-system! To further maximize filtration, and also make koi more conformable, you can also consider adding a dedicated air pump so your waters are highly oxygenated ready for warmer weather.
For more details on our spring koi pond routine and what you should consider, check our full guide on spring maintenance here!