Hong,
What are you talking? 16 months to grow to 45cm-50cm? That's a bit to long with bacteria house and bakki showers! Give me 6 months will do! Tosai from 20+cm reach almost 50cm within 6-8 months with bacteria house and bakki showers!
Hey Tai goh
16 months is the age of the koi, when I bought it at 4 months old only around 11 or 12 cm (some of them) 1 year on its 48.5cm that is with 6 month growing season and additional 2.5 months heated 1 ton pond. Remember its aussie koi not good genetic japanese koi
You forgot to mention you do that with a 10 ton pond and about 35 to 40 koi around 40 to 75cm
tewa