You have to collect food and free at last Karla (or Karl) from a thicket of plants in 6 levels of play. The faster you can do this and if you have eaten all the food, you will become a Grand Champion - the highest award for a koi.
At level 1, it is cozy. Eat the food. It is not distributed widely and you'll find it in the first area of the pond.
In the 2nd Level, you can focus on the first area of the pond, too.
Perhaps you have already discovered the access to the second area of the pond. It is hidden by stones. But with a little skill you can swim through the stones. The bigger you get, the more difficult it is, of course ;-)
Now you have a considerable size. Focus on the first two areas of the pond.
Now you have to search for food in the entire pond with its three areas. Now it turns out if you have learned to find the food fast enough. Otherwise, you're running out of energy.
Karla (or Karl) is wating for you. Of course in the third area of the pond ;-)