What a Coypu Rat should eat changes across its life more than most owners expect. Portion size, not brand, is where most first-year problems start.
A breed from South America, living in India
The Coypu Rat was developed in South America. The part that travels badly is rarely temperament - it is the coat and the tolerance for heat. Plan the year around that and most of the rest follows.
The basics
For a Coypu Rat, unlimited hay or the species staple is the foundation, not a supplement. The teeth grow continuously and the gut depends on constant fibre.
Changing food
Phase any change over a week. An abrupt switch upsets the gut and tells you nothing about whether the new food suits a medium animal.
Measured, not topped up
Pellets are portioned. Fresh vegetables daily in small amounts. Sugary treats and most fruit are a bad idea for the smaller species.
Balancing calm against semi-aquatic
Breeds described as both calm and semi-aquatic need the two managed together rather than separately. With a medium animal that usually means a predictable routine first and training second - the routine is what makes the training stick.
Storage in an Indian climate
Humidity spoils dry food faster than the printed date suggests. Smaller quantities through the monsoon, sealed, and look at it before it goes in the bowl.
Planning for about 7 years
A Coypu Rat is with you for about 7 years. Budget and routine both need to survive that, including the last quarter of it when a medium animal needs more veterinary attention than it did young.