What is the difference between grass carp and koi? A quick guide to telling them apart

Carp usually inhabit the bottom layer of rivers, lakes, reservoirs and ponds where aquatic plants grow thickly. There are many varieties, among which koi are ornamental fish and are easily confused with grass carp. So, what is the difference between grass carp and koi?

1. What is the difference between grass carp and koi?

1. Body shape: grass carp are slender, with the dorsal fin set far back, while koi are somewhat rounder and plumper, with the dorsal fin set forward;

2. Color: grass carp come in many colors, including black, gray, orange, gold, and also variegated ones, while koi are mainly red and white;

3. Barbels: koi have barbels, while grass carp do not.

2. How do you keep koi?

1. Dechlorinating the water for rearing

Tap water is generally the most commonly used water for koi keeping, while river water, well water and spring water are rarely used to raise koi. However, no matter which water quality it is, it contains a certain amount of chlorine. So dechlorinate before use. There are generally two methods: the first is chemical dechlorination: put an appropriate amount of sodium thiosulfate into the water, and it reacts with the chlorine to form harmless sodium salts. The second is physical dechlorination: leave the water in the sun for two or three days, or keep aerating the water to “drive off” the chlorine

2. Water quality indicators

The water for keeping fish must be colorless and transparent, with no turbidity; as for temperature, 22~28℃ is best, and sudden temperature changes should be avoided as much as possible, with a difference of no more than 2℃, otherwise it will directly harm the health of koi; when the normal dissolved oxygen level reaches 5~7mg/L, it is relatively suitable for koi keeping conditions; koi are suited to growing in weakly alkaline water, so an alkalinity of around 6~8.5 is normal; the ammonia and nitrogen content in the water must not exceed 0.1mg/L, otherwise it will threaten the health of koi. Chemical substances such as ammonia nitrogen are harmful to aquatic organisms, and too high a content will directly cause koi death.

3. Bait and feeding

In the choice of bait, it is generally divided into natural bait: bloodworms, earthworms, mealworms, etc.; artificial bait: growth feed, germ-based feed and color-enhancing feed, etc. When feeding, it is best to follow the “four fixed principles”: fixed time, fixed place, fixed quality, fixed quantity, to develop good eating habits.

4. Rearing management

Stocking density: koi also have requirements for stocking density. For example, the density for an aquarium is generally 60 cubic cm × 30 cubic cm × 15 cubic cm, and such an aquarium can keep 6 koi with a body length of 15 cm to 20 cm. 90 cubic cm × 30 cubic cm × 50 cubic cm can hold 8 fish. 110 cubic cm × 30 cubic cm × 50 cubic cm can hold 10 fish.

Timely inspection: if the koi's feces become white and gelatinous, it is a danger signal of intestinal mucosa shedding, and if not treated immediately, gastrointestinal perforation disease will occur. When koi have indigestion, fish feces lighter than the pond water will appear on the water surface; stop feeding immediately and observe.

In addition, when keeping koi, their excrement needs to be cleaned up in time and the fish tank must be kept clean. If it is a fully automatic fish tank with a built-in cleaning system, changing the filter cotton or cleaning it once every half a month is enough.