Fishbase -
https://www.fishbase.se/summary/SpeciesSummary.php?ID=1450&AT=koi Food items - see about 10 lines down - fish eggs/fry
https://www.fishbase.se/TrophicEco/...43&genus=Cyprinus&species=carpioreproduction:
Spawn in marginal, shallow, weed-infested areas. A polytypic plastic species with a marked tendency to produce `varieties' and `races' in response to selective breeding and environmental influences. Carp is polygamous. A spawning female is usually followed by several males. Under tropical conditions carp breeds throughout the year. It is a seasonal spawner in temperate waters (Ref. 185).
Females are known to lay more than a million eggs in a season; breeds at a temperature range of 15° C to 20°C; eggs hatch in 4 days (Ref. 6028). Obligatory plant spawners (Ref. 7471). "Adults often make considerable spawning migrations to suitable backwaters and flooded meadows. Individual females spawn with a few males in dense vegetation.
The sticky eggs are attached to water plants or other submerged objects. Reproductive success is restricted to years when the water level starts rising in May and when high temperatures and flooding of terrestrial vegetation last for a long period during May and June" (Ref. 59043).