Koi fish are fascinating fish with a rich cultural and biological background.

1. Symbolism in Japan

In Japan koi represent perseverance, strength, and longevity. According to legend, a koi that swam upstream and transformed into a dragon after leaping over the Dragon Gate waterfall symbolizes determination and success.

2. Long lifespan

Koi can live for an incredibly long time—sometimes over 50 years, and in some cases, even up to 200 years. The oldest known koi, named Hanako, lived to be 226 years!

3. Colour Variety

Koi come in a wide range of colours, including red, orange, yellow, white, blue, and black. Each colour and pattern can have a specific meaning. For instance, a red koi is often associated with love and passion, while a white koi can represent purity or new beginnings. The most common varieties are the Showa, Sanke, Kohaku and Goshiki.

4. Grow large

Koi can grow quite large, with some varieties reaching up to 3 feet (90 cm) in length. This makes them one of the largest ornamental fish in the world.

The world's biggest koi fish was named Big Girl, weighing 40kg and is 120cm long.

5. Intelligent Fish

Koi are known for their intelligence. They can recognize their owners and even learn to respond to certain stimuli, like being fed or approaching the pond. Some koi will even follow their owners around the pond.

6. Social Creatures

Koi are social fish and often thrive in groups. In fact, they tend to be more active and healthy when kept in schools rather than alone.

7. Originating from Carp

Koi are actually a type of carp (Cyprinus carpio) and were selectively bred in China and Japan for their bright colors. Over generations, these carp became what we know as koi today.

8. Loyal to their pond

Koi can develop a sense of loyalty to their environment. They often return to the same spots in the pond and may be resistant to changes in their surroundings.

9. Breeding

Koi are prolific breeders and can lay thousands of eggs during each breeding season. However, only a small percentage of these eggs will survive and grow into adult koi, as they face many challenges like predators and competition for food.

Maintaining the right water parameters is essential for the proper growth and overall health of koi fish.

Here are the ideal water parameters for keeping koi:

1. Temperature

Ideal Range: 18°C to 24°C.
Tolerable Range: 10°C to 29°C.
Koi can survive in a wide temperature range, but they thrive best in moderate temperatures.

2. pH Level

Ideal Range: 7.0 to 8.0
Koi prefer neutral to slightly alkaline water. Avoid pH levels below 6.5 or above 8.5.

3. Ammonia (NH₃)

Ideal Level: 0 mg/L
Ammonia is toxic to koi, so it should always be at zero. Regular testing is necessary to monitor ammonia levels.

4. Nitrites (NO₂)

Ideal Level: 0 mg/L
Nitrites are also harmful to koi. They should also always be kept at zero.

5. Nitrates (NO₃)

Ideal Level: 20–40 mg/L
Nitrate levels are less toxic but should be kept under control with regular water changes and a good filtration system. Aquatic plants such as the water Hyacinth and water lettuce are good nitrate sinks.

6. Hardness (GH)

Ideal Range: 100–300 mg/L
Koi prefer moderately hard water. This provides essential minerals such as calcium, for proper bone development and general health.

7. Alkalinity (KH)

Ideal Range: 80–150 mg/L
Alkalinity buffers the water's pH and prevents it from fluctuating rapidly. 

8. Dissolved Oxygen

Ideal Level: Above 6 mg/L
Koi need well-oxygenated water for healthy gill function, especially in warmer temperatures. Air compressors, pumps and water falls all contribute to a higher amount of dissolved oxygen.

9. Filtration

Ensure a high-quality filtration system is in place to handle the bio-load, as koi produce a lot of waste. A combination of mechanical, biological, and UV filtration is recommended.

10. Water Movement

Koi prefer gentle water movement with good circulation. This helps oxygenate the water and prevent stagnant areas.

Poor water quality can cause diseases or even shorten their lifespan.
Regular monitoring (using test kits) and maintenance of these parameters will help ensure a healthy environment for your koi.

Koi fish are susceptible to a variety of diseases, most of which are caused by poor water quality, stress, or weakened immune systems.

Here are some of the most common koi diseases:

1. Ich (White Spot Disease)

Cause: Protozoan parasite (Ichthyophthirius multifiliis).
Symptoms: White, grainy cysts on the skin, fins, and gills. Fish may rub against surfaces and display rapid gill movement.
Treatment: Add 1g/L deionised rock salt every day over 5 days to have a total of 5g/L. Wait for 21 days. Filtration must be bypassed. After 21 days reduce salt concentration gradually by carrying two 50% water changes over 3 days. Salt water must be discarded as it would otherwise kill land plants.

2. Koi Herpesvirus (KHV)

Cause: A highly contagious viral infection.
Symptoms: Lethargy, rapid gill movement, lesions on the skin, and fish may swim erratically.
Treatment: No cure; prevention is key, and affected fish should be isolated.

3. External Bacterial Infections (Aeromonas or Pseudomonas)

Cause: Bacteria that infect open wounds or weakened fish.
Symptoms: Ulcers, red or inflamed areas on the skin, and fin rot.
Treatment: Antibiotics or antibacterial treatments, along with improving water quality. A 3g/L rock salt water treatment will help wound healing without effecting the biofilter.

4. Fungal Infections

Cause: Fungi such as Saprolegnia, often infecting fish with damaged skin.
Symptoms: White, cotton-like growth on the skin, especially near wounds.
Treatment: Antifungal treatments e.g Malachite green on effected area and improved water conditions.

5. Costia

Cause: Protozoan parasite Costia that affects the skin and gills.
Symptoms: Lethargy, rapid gill movement, flashing, excessive mucus production, and skin lesions.
Treatment: Formalin or potassium permanganate treatments.

6. Gill Flukes (Dactylogyrus)

Cause: Parasitic flatworms that infest the gills.
Symptoms: Excessive gill movement, lethargy, and reduced feeding,flashing.
Treatment: Fluke Solve.

7. Dropsy

Cause: Internal bacterial infections or organ failure.
Symptoms: Swelling of the body, raised scales (pinecone appearance), and bloated abdomen.
Treatment: Antibiotics or 3g/L salt water for 15 days.

8. Swim Bladder Disorder

Cause: Can result from internal bacterial infections, trauma, or poor water conditions.
Symptoms: Difficulty swimming, floating upside down, or swimming erratically.
Treatment: Varies based on the cause, but may include improving water quality or anti-bacterial treatments.

9. Chilodonella

Cause: Protozoan parasite that affects the skin and gills.
Symptoms: Heavy and rapid gill movement , flashing and rubbing, skin cloudiness caused by excess mucus, loss of appetite and lethargy.

Treatment: Potassium permanganate(PP) 1.5 grams per 1000 liters. Keeping the
water purple for 4 hours, additional 1/4 or 1/2 doses may be required in ponds with heavy bio load. When water starts to go brown the PP is spent and not doing anything else. To neutralise PP add Hydrogen Peroxide (30ml of 3% peroxide for 500 litres pond water). Always add lots of extra air to a pond when treating
with PP as it is an oxidising agent. Where possible avoid feeding for 24 hours prior to using PP. It is usually a good idea to do a deep clean of the filers and system to avoid
having more organic matter in the pond for the PP to consume.

10. Koi pox

Cause: Herpes virus
Symptoms: Waxy whitish mole like structures on skin, generally around the mouth and on fins including the tail.
Treatment: Warm water and good water quality. No medication.

Preventing koi diseases

This involves maintaining good water quality, regular pond maintenance, avoiding overcrowding, and proper quarantine procedures for new fish.

Potassium permanganate dip

This is very effective for most protozoan  parasites and bacteria. Use 1 gram PP per 10 liters of pond water for 7 minutes. Always aerate and ALWAYS remove the fish if it gets restless and jumpy. Control timing precisely and do not treat too many fish at the same time unless you can time the treatment of each fish correctly.

If a koi shows signs of illness, it's important to act quickly to prevent further spread or complications.

Feeding Koi fish properly is key to keeping them healthy and vibrant.

Here are some tips:

Choose the Right Food

Use high-quality (high protein in summer and wheatgerm in winter), well-balanced koi pellets or flakes, specifically designed for koi. These foods contain the right mix of nutrients, including proteins, vitamins, and minerals. You can also supplement with treats like fruits, vegetables (e.g., lettuce, peas, or watermelon), and earthworms occasionally.

Feed in Moderation

Overfeeding can lead to water quality problems and obesity in Koi. Feed them only what they can consume in 3 minutes, once or twice a day. In very hot (higher than 28°C) and in colder months (below 10°C), stop feeding. Koi metabolism slows down and these fish are not tropical.

Variety is Key

In addition to pellets, koi enjoy a variety of foods, such as spirulina, wheat germ, and even small live foods like daphnia. A diverse diet will enhance their color and health.

Amount of food

2% of total body weight twice a day at a water temperature 22-24°C. For other temperatures and frequency of feeding visit koimalta instagram page.

Feeding when koi are sick

Koi should not be fed if they’re stressed or showing signs of illness. Always ensure the water quality is good before offering food.

By following these tips, you can help your Koi thrive and maintain their stunning appearance