The selection and management of water for koi fish cultivation require comprehensive consideration of water source characteristics, water quality treatment, and daily maintenance. Below are specific key points and operational recommendations:
I. Water Source Selection and Characteristic Analysis
Tap Water
Advantages: Convenient access and low bacteria content, making it suitable for home cultivation.
Disadvantages: Contains chlorine-based disinfectants. Direct use can cause gill congestion, mucosal damage, and even death of koi fish.
Treatment Recommendations:
Aeration Method: Place tap water in an empty basin or pool, expose it to sunlight for sedimentation for 24-48 hours (can be shortened to 12 hours in summer) to make the water temperature close to the air temperature and allow chlorine to evaporate.
Chemical Method: Use sodium thiosulfate (hypo). Add 2-3 grams per cubic meter of water to neutralize chlorine. However, pay attention to the dosage—excessive use or use under high temperatures can easily cause water turbidity.
Well Water
Advantages: Stable hardness, suitable for rural areas in northern China.
Disadvantages: Hardness may exceed the standard (e.g., the hardness of well water in Hengshui area reaches 300 ppm), requiring adjustment after testing.
Treatment Recommendations:
Test the hardness. If it exceeds 16° (medium hardness), add volcanic rock, almond leaves, or water softeners (such as trisodium phosphate, EDTA) to reduce hardness.
Test water quality weekly to ensure hardness remains stable between 8-16°.
River/Lake Water
Advantages: Natural water source rich in plankton.
Disadvantages: High levels of impurities and pollutant risks, requiring complex filtration.
Treatment Recommendations:
Adopt three-stage filtration: 60-mesh stainless steel screen to intercept impurities → activated carbon to adsorb pollutants → ultraviolet sterilization.
Regularly test the content of ammonia nitrogen and nitrite to ensure compliance with fishery water quality standards.
Rainwater
Advantages: Low cost, suitable for large fish ponds.
Disadvantages: The pH value of initial rainwater is low (can reach 5.3), which harms fish gills.
Treatment Recommendations:
Collect middle-stage rainwater (avoid the first 10 minutes of initial rainwater), filter it with gauze, and mix it with mineral water at a ratio of 10% to supplement minerals.
Purified Water
Disadvantages: Long-term use can cause electrolyte imbalance in koi fish and fin rot.
Treatment Recommendations:
Mix with 1/3 treated tap water or add mineral powder to balance electrolytes.
II. Core Indicators for Water Quality Management
Water Temperature
Suitable Range: 5-30℃, with the optimal growth temperature being 18-28℃.
Precautions: A sudden temperature change of more than 2-3℃ can cause stress in koi fish. Insulation is required in winter (by deepening the water level or heating), and oxygenation is needed in summer to prevent oxygen deficiency.
pH Value
Suitable Range: 7.0-7.5 (slightly alkaline).
Precautions: A pH value below 7 will cause koi fish to become less active, have poor appetite, and dull body color; a pH value above 8 will affect growth and even lead to death. Regular testing is necessary, and adjustment can be made with quicklime or acetic acid.
Dissolved Oxygen
Suitable Range: 5-8 mg/L, with a minimum of 3 mg/L.
Precautions: Insufficient dissolved oxygen can cause koi fish to surface for air and even suffocate. Oxygen can be supplemented through aerators, aeration, or adding new water.
Hardness
Suitable Range: 8-16° (soft water or neutral water).
Precautions: Excessively high hardness will affect the reproduction of koi fish (reducing the hatching rate of fertilized eggs). Distilled water, water softeners, or trisodium phosphate can be used to reduce hardness.
Harmful Substances
Ammonia nitrogen and nitrite: Should be close to 0. Regular testing is required, and control can be achieved through water changes, filtration, and decomposition by nitrifying bacteria.
Hydrogen sulfide: Generated when there is excessive sludge at the bottom of the pool. Regular pond cleaning and disinfection are necessary.
III. Daily Maintenance and Operational Recommendations
Water Change Frequency
Partial Water Change: Replace 1/4-1/3 of the water volume weekly to stimulate the fish's appetite and improve water quality.
Complete Water Change: A major taboo! It will destroy the ecosystem and should only be used in emergency situations (such as disease outbreaks).
Precautions: Control the temperature difference between new and old water to 1-2℃ to avoid stress in koi fish.
Filtration System
Recommended Configuration: Drip filtration and bottom filtration combined with physical filter cotton and biochemical filter media (such as coral stone, activated carbon, zeolite).
Maintenance Recommendations: Regenerate zeolite monthly (soak in saturated salt solution for 48 hours) and clean the filter media regularly.
Feed and Feeding
Feed Selection: Mainly use special koi feed, with occasional addition of vegetables and fruits.
Feeding Principles: Feed small amounts multiple times, 2-3 times a day, and ensure the feed is eaten within 5 minutes each time to avoid water pollution.
Fasting Temperature: Stop feeding when the water temperature is below 10℃ to prevent indigestion.
Disease Prevention
New Fish Quarantine: Isolate and observe new fish for 2 weeks before putting them into the tank to prevent the introduction of parasites or pathogens.
Regular Disinfection: Use 3% salt water for medicinal baths to prevent surface infections.
Anti-Stress Treatment: When the weather changes suddenly or water quality deteriorates, spray "Detoxification and Anti-Stress Agent" to relieve stress.
IV. Seasonal Adjustments
Spring: As the water temperature rises, increase the feeding amount and conduct regular disinfection.
Summer: Increase oxygen supply to prevent oxygen deficiency and control algal blooms.
Autumn: Reduce feeding and prepare for overwintering.
Winter: Keep warm to prevent freezing and reduce the frequency of water changes.