I. Determining Appropriate Stocking Density
The first step in setting up an ecological aquarium for koi is to establish the stocking density. Due to their large size and high waste production, maintaining water quality is challenging. Therefore, stocking density becomes the first line of defense in preserving water quality. The recommended stocking density in an ecological aquarium is 1 liter of water per 1 centimeter of koi length. This means if your aquarium holds 150 liters, you can stock koi with a total length of 150 cm, which is approximately 15 koi each measuring 10 cm in length.
II. Scientific Feeding Practices
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Feeding MethodsKoi are naturally gentle and do not shy away when people approach, making feeding time an excellent opportunity to observe them. If you feed at a fixed location or provide a signal—such as playing music or gently tapping the aquarium—they will gather at the feeding spot in anticipation, and may even eat directly from their keeper's hand.
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Feeding Amount, Timing, and FrequencyDetermine the feeding amount based on the koi's appetite and digestion, avoiding overfeeding. Adjust accordingly when feeding dry food, bran, bean cake, or formulated feeds. If the weather is clear, dissolved oxygen is sufficient, and the water temperature is suitable for normal koi activity, slightly increase the feeding amount. On overcast days or when conditions are闷热 (stuffy) with low dissolved oxygen, leading to reduced appetite, feed less. Koi that are gasping at the surface or are sick should be fed sparingly or not at all. Delicate and valuable species should also be fed moderately. The color of koi feces can indicate their condition: green, brown, or black feces suggest appropriate feeding and good digestion, while white or yellow feces indicate overfeeding, and feeding should be stopped immediately.Feeding times depend on the type of feed. Live feed is typically given once early in the morning after sunrise. In autumn and winter, feeding can be delayed by 1–2 hours, and during severe winter, a small amount can be offered at noon. For dry and formulated feeds, provide an amount that can be consumed within 1–2 hours. The number of daily feedings should be adjusted according to the koi's health, water conditions, and water temperature, with water temperature being the most critical factor. The optimal water temperature range is 22–25°C, with 3–6 feedings per day following the principle of small, frequent meals.
III. Maintaining Good Water Quality
The ideal water quality for keeping koi is neutral water with a pH of 6.7–7.5, optimally between 7.2 and 7.4. The dissolved oxygen (DO) level should be maintained at 6–8 mg/L. For an ecological koi aquarium equipped with a bottom drainage system, perform a water change of about one-third once a week.
IV. Preventing Koi Diseases
Relatively speaking, an ecological koi aquarium is a stable micro-environment, so diseases are generally uncommon. Therefore, quarantining new fish before introduction is particularly crucial. Once pathogens are introduced, all koi in the aquarium are at risk of infection.
(1) When selecting koi, choose individuals with bright colors, well-proportioned body shapes, high activity levels, and no visible injuries. A koi that looks attractive is generally healthier.
(2) Strengthening Prevention Measures: Place new koi in a small quarantine tank and treat them with fish disease preventive medication for three days without feeding. Observe for any symptoms during this period. If symptoms appear, administer appropriate medication immediately. Only after passing this quarantine stage should the koi be introduced to the main aquarium. Additionally, introducing koi in batches is another effective disease prevention method. For example, if planning to keep 10 koi in the ecological aquarium, introduce them in three batches, ensuring each group is healthy before adding the next.
(3) Handling External Parasites: Newly acquired koi often carry external crustacean parasites such as fish lice (Argulus) or anchor worms (Lernaea), as most koi farms use outdoor concrete or earthen ponds where such infections are common. The treatment method involves directly adding medication designed to kill external parasites to the ecological aquarium.
(4) Enhancing Care: Regularly observe changes in the koi's body surface, swimming behavior, and any deviations from normal patterns. Most diseases manifest symptoms on the body surface, with parasites being particularly easy to spot. Other signs, such as skin redness or fading colors, also indicate potential health issues.
V. Timely Cleaning of the Aquarium Walls
Before performing a water change, if you notice waterlines at the water-air interface on the aquarium walls or green algae on the substrate, clean the walls promptly to remove the algae. Use a clean filter sponge to gently wipe away the waterlines and algae, then proceed with the water change.
VI. Pruning Aquatic and Terrestrial Plants
An ecological koi aquarium typically contains both terrestrial plants above water and aquatic plants below. These should be pruned differently:
(1) Pruning Terrestrial Plants: Remove any yellowing or dead leaves immediately by gently plucking them or using specialized pruning shears. Apply foliar fertilizer as needed. If terrestrial plants become overly lush and overshadow the aquarium's main features, control their growth by trimming, focusing on cutting back the tips and long-growing branches.
(2) Pruning Aquatic Plants: If you notice dead or wilting aquatic plants, promptly trim them using dedicated aquatic plant scissors and apply liquid fertilizer as appropriate.
