"How does the seahorse work?

Once a long held mystical secret from the land of Isola, we have discovered the golden seahorse's fantastic power in Fish Tycoon 2. Owning the seahorse increases the likelihood of a customer purchasing a fish. The seahorse does not take up tank space."

Taken from the Research and Upgrades page of Last Day of Work's Fish Tycoon 2. Sounds legit. Sounds even more plausible when you take into account that Tanks 1 and 2 hold 20 fish but the Sell tank holds 21. Since we know that the Seahorse takes up 1 space, it makes sense. Almost like the developers were dropping us hints that the Seahorse works its magic in the Sell tank.