Every time you eat a prey, you gain a little experience. With enough experience, you’ll gain a level, and when you do, you can use that experience to improve an attribute of your koi
Experience is shown in the circle around your level number. When it’s full, you will reach a new level and have Ability Points to allocate to one of your attributes.
So the example below, I have 3 ability points that I can put into Agility, Speed or Rarity.
Here’s my understanding of what the attributes do, and please add to the comments if you have any thoughts on this.
This stat modifies how quickly you can turn, and if improved will help you catch prey much faster. This is what I recommend you put the majority of ability points in at the beginning. Agility also improves the “lunge” when you try to catch a prey.
Simply – how fast you can swim. At the beginning, most prey will be faster than you, so you’ll need to get this up to a reasonable level to make your life easier.
This seems to improve the chance that your rare color will be passed on to your offspring. So if you’ve got a koi with a common color, you can prioritize the other two stats over this. However, if you find a rare color, you can spend all of your points on this stat to make sure you get lots of rare-colored offspring.