Tip 1: Your koi can grow from a kid to an adult by eating other fish in the pond. You can either tap on a specific spot in the pond to go there, hold your finger in a specific direction in order to go in that direction, or tap on a fish to track it until you eat it. That's the easy way to level up, so tap on a fast fish to track it almost endlessly, eating other fish in the process.

Tip 2: You can breed with other koi too when you find them. When they pop up, stay near them and keep them in your circle. When you fill the circular bar all the way, you and your other koi will make an egg. You can either hatch it right away for pearls, or you can send it to your egg stash, where it will unlock with time.

Tip 3: The more that you expand your pond, the more different fish that you can find and eat. The later that you unlock a type of fish, the more it will add to your experience points, allowing you to add to your stats faster. Each time that you expand your pond, new fish will appear.

Tip 4: To expand your pond, you need to craft different symbols. To do this, tap on the bubble icon in the lower right corner of the screen. You'll either see things that you can craft, or you'll see what you need to eat in order to do the crafting that you need to do in order to complete the expansion.

Tip 5: When you are focused on breeding a rare koi, upgrade your rarity stat above everything else, with only as many speed and agility upgrades as you need to keep up with faster fish and other koi. You can reverse the points that you have spent up until the point that you close out of the menu and lock in the upgrades.