How to adjust NPK levels thru feed

[Elan yadan]

How could I adjust NPK levels? I'm assuming its a plants/meat ratio. What produces more of which? Plants high N, meat high PK?? or vice-versa. I plan on feeding the fish and turtles live worms and lettuce and fruits (yes my goldfish nibble on pears and fruits) and a staple of high-quality pellets. Trying to stay as organic as possible. Thanks