I bought 5 terrapins in the past , now left 2. They should be
over 10 years , forget about the exact year.
2 died cos' of skin problem ( bacteria infection ), 1 died of
obesity ( i suspect ). 2 still alive.
Small terrappins need clean water cos' their immune
system not as strong as adult terrapins.Feed them only what they
can consume within 5 minutes.They feed on dried shrimps and
lot of vegetables. They only consume food that floats on water
, they need basking , some space for them to explore( they are
highly curious creatures) , a dark shade to sleep in , some water
for them to swim in maybe( to exercise ). They need warmth cos'
they cant regulate their own body temperature. They recognise their
owners.
Your terrappin could die of illness or face chronic stress
living with koi , koi consume all the food in the pond or
unsuitable food for the terrappin.