Apart from Moby Whale, another secret fish called Baby Pond Emperor was added to Fisch as part of the Whale Migration Event. Many players did not know about this fish as they were not included in the update log, and everyone was busy hunting the Whales. So, if you don't know how to get the Baby Pond Emperor, here is a detailed guide about the process.
You can find and fish for the Baby Pond Emperor in the Lake of the Snowcap Island, aka Snowcap Lake or the Upper Snowcap. So, get on your boat and travel straight to the GPS location (2809, 280, 2563) to reach the island. Here, make your way slowly across the mountain to reach the lake. If you don't know how the lake looks, you can refer to the above image.
Now, it is time to fish for the Baby Pond Emperor in the game. For the requirements, refer the list below.
Since the Baby Pond Emperor has a nearly -80 % Progression Speed rating, I recommend you use a good rod like Forsaken, Rod of Depths, Ethereal Prism, or even the Poseidon. That's all with the requirements! Now, you have to be patient and keep fishing. With time and effort, you will get the Secret Baby Pond Emperor and finish your Bestiary for Snowcap Island.
For more on Fisch, Check out All Brick Rod Titles and Timing Requirements – Fisch or How to get Song of the Deep Relic in Fisch – Blessed Song Enchant
