(1) Phytoplankton
Microscopic algae that serve as excellent feed for koi fry. Koi digest diatoms, chrysophytes, and yellow-green algae well; they can also digest green algae and dinoflagellates but cannot digest euglenoids and blue-green algae. Phytoplankton inhabits various small puddles, ponds, ditches, rice fields, rivers, lakes, and reservoirs, often turning the water greenish-yellow or dark green. They can be collected using a fine-meshed net and fed to koi.
(2) Filamentous Algae
Commonly known as "pond scum" or "green algae," these primarily consist of multicellular green algae, typically dark green or yellowish-green. Koi usually do not eat attached filamentous algae as they tend to be tough and coarse. They prefer free-floating filamentous algae such as Spirogyra, Zygnema, and Mougeotia, which are soft and smooth. These algae are found in shallow areas of ponds, ditches, lakes, and rivers and are widely distributed. Filamentous algae should only be fed to larger koi.
(3) Wolffia (Watermeal)
Also known as duckweed or rootless duckweed, it is a perennial floating plant found in small ponds, rice fields, lotus ponds, and stagnant ditches. It is highly effective for feeding koi.
(4) Common Duckweed (Lemna minor)
A perennial floating plant usually growing in stagnant waters such as rice fields, lotus ponds, and ditches. It can be used to feed larger koi.
(5) Spirodela polyrrhiza (Giant Duckweed)
Purple-backed duckweed, commonly found in stagnant waters like rice fields, lotus ponds, ponds, and ditches. It lacks trace elements like cobalt and does not promote growth in koi.
(6) Vegetable Leaves
Leafy greens should not be a staple in a koi's diet but can be offered as a supplementary source of vitamins. Koi enjoy tender bok choy and lettuce leaves. Before feeding, ensure leaves are thoroughly washed and soaked in clean water for at least 30 minutes to remove any pesticides or fertilizers that could cause poisoning. Chop the leaves into fine strips appropriate for the size of the fish.
(7) Spinach
Fresh spinach should be washed, blanched in boiling water, and finely chopped before feeding. Rich in vitamins, spinach helps enhance the koi's constitution and should be regularly added to their diet.
(8) Tofu
Soft and easily consumed by koi of all sizes, tofu is a suitable feed. However, during the hot summer months, leftover bits can decay rapidly, degrading water quality. It should be fed sparingly or avoided to prevent residue accumulation.
(9) Cooked Rice Grains and Noodles
Koi can digest various starchy foods. Break dry noodles into pieces and soak in boiling water until partially cooked, or boil briefly and rinse with cold water to remove surface starch before feeding. Cooked rice should also be rinsed to remove fine particles before offering.
(10) Biscuits, Steamed Buns, Bread, etc.
These can be crumbled and fed in small quantities. Similar to rice and noodles, uneaten particles and waste produced after consumption can suspend in the water as non-settling colloidal particles, clouding the water and potentially causing low oxygen or hypoxia.
