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Koi feeding at the water surface

Sink or Swim: Floating vs Sinking Koi Food

Any pet owner will attest to a certain amount of anxiety about which type of food is best suited to their pet. There are quite literally hundreds of choices for koi food available on the market. And the philosophies as to which is best is also a hotly debated topic.

It is not only the brand that an owner has to consider, but also whether it stays on the surface of the water or sinks to the bottom.

Being set up as bottom feeders with downward facing mouths, it makes sense that something that sinks to the bottom of the pond would make it easier for the koi to feast. But they are equally as adept at picking food off the surface.

So which is better? Many enthusiasts will use a combination of both. Each has its own virtues as well as its drawbacks. Here’s a look at each of the types of food and how they stack up.

Sinking

As the name suggests, this is a pellet made at higher pressures, making it more dense so that it sinks to the bottom where the natural feeding habit of the koi in question can chow down. Literally. This one thread speaks to the use of using sinking pellets in Japanese dealers ponds to help males bulk up.

Koi Forum post regarding sinking koi food

Pros

  • Better nutritional content for the koi. It is denser and more packed with a higher concentration of nutritional ingredients meaning that the koi get more nutrients for less work.
  • Good for shy or smaller fish who might not feel comfortable or safe closer to the surface.
  • Also good in faster moving streams.

Cons

  •  The feeder is not entirely sure that the amount they are feeding is too much or too little.
  • Ends up in the bottom filter before it is eaten. One strategy to stop the food getting into the bottom drain is to stop the flow of the pond by temporarily turning off any features (waterfalls, bubble bottom drains/domes) that cause water to circulate while the koi are feeding.
  • It can end up lost on the bottom or won’t get consumed in time where it degrades and affects water.
  • Your koi are not as visible as they could be if they were feeding at the surface.

Floating

Again, the name kinda gives it away. This is a lighter, less dense pellet made at lower pressures (sometimes with a baked outer shell) that will float until it becomes saturated and will eventually sink.

Pros

  • You can see your aquatic babies up close and personal.
  • You can inspect your koi for any signs of illness at the surface as they feed.
  • Smaller koi (if not in a secluded set up) might not always come to the surface (except maybe the chagoi, a meal is a meal is a meal to them—and they are quite often the first to learn how to hand feed). This is your chance to see them frequently.

Cons

  • Gulping at the surface means they are more likely to take in “regular” air, which can be a contributing factor in swim bladder disease.
  • In ponds with fast moving surface current the pellets can get into the skimmer before the koi ever get to eat it. One way to address this is through feeding rings where the food is kept without being swept away in the current. They are an inexpensive way to keep your koi food from floating away, while conditioning your koi to feed in the same place repeatedly.

Of course, this doesn’t tell the full story as there are other aspects of feeding to consider, too.

Amount of Food

To combat the amount of food that ends up either in the skimmer, substrate or bottom drain, the amount of food that is either floated or sank is an important factor. Overfeeding will result in the type of waste that causes bottom drains and skimmers to fill up as well as a deterioration of water quality.

The general rule of thumb is to feed your Living Jewels as much as they can eat in five minutes. Once you get to know your koi better you will be able to tailor the amounts and the feeding schedule to suit their needs. The size of your koi will also dictate how much you need to feed as well as the size of the pellets you will need to use. Smaller koi require more protein more often to grow in optimal feeding conditions.

Water Temperature

The amount and frequency with which you feed your koi is largely based on the ambient water temperature. As cold-blooded fish, their metabolism is dependent on the temperature that they are in. The higher the temperature, the more you can feed them. The inverse is also true. Lower temperature, lower frequency and less food.

As water temperatures increase, the amount of protein should be increased until it is at about 40% of their diet in the warmest months. In cooler temperatures, higher carbohydrate-to-protein ratios should be observed until it is cold enough not to feed at all. Here is a guide for feeding koi according to temperatures as well as food types.

Food Types

Types of food, high-protein, wheat germ and growth are going to depend on the age of the fish, the season as well as what the owner is trying to accomplish. Protein is essential to help the koi grow as well as sustain many of the necessary repairing cellular functions. Carbohydrates (with wheat germ) are a good way to keep the metabolic functions ticking over in cold temps and are a fine source of Vitamin E.

There are numerous proprietary blends of food available. Some enthusiasts go so far as to make their own. There are varying pellet sizes too and this is helpful in digestion for koi of various sizes in the pond. Flakes can be helpful for your smaller koi.

How Food is Made

Hundreds of koi fish waiting for koi food

Koi Carp feeding time, by Richard Barton cc 2.0

Most modern koi pellets are made in the same way. A “batter” is made with most of the ingredients being folded into a dough under higher heat with moisture. In a previous post, we took a look at some of the ingredients used in koi food.

This is then pushed through an extruder (similar principle to a meat grinder) under differing pressures. This is what determines whether or not it floats. The denser pellets (squeezed out under high pressures) will sink. The less dense pellets (which are sometimes steam baked to create a buoyant shell) will then float.

The pellets are cut to size as they come out after which they are dried and necessary fats and oils are added. The fat helps to keep the pellets from degrading as quickly as well are easily digested by koi.

Ultimately, your koi will tell you which food they prefer, both in the type, style and amount. You can also give them treats of fresh fruit like watermelon, orange slices as well as cheerios, earthworms, silkworm pupae and prawns. A proper diet is important in a koi’s long-term health, so be patient and get it right.

2 Responses to Sink or Swim: Floating vs Sinking Koi Food

  1. Charles Benninghoff March 31, 2017 at 12:25 pm #

    Thanks for the idea about the floating feed ring. Looks like it will work.

    Do you think just a ring is OK or is the bottom “skirt” an essential part?

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