Feeding fish certainly required manpower; with over a hundred acres of lake surface, and fish fry worth hundreds of thousands, they needed to eat every day. Even with automatic fish feeders, someone needed to regularly add feed and operate the machines.
But Suming was unwilling to hire additional staff just for the sake of feeding fish.
After all, contracting Shuijun Lake was about doing business to make money, not charity. In a mutually beneficial situation, he was willing to contribute to the zoo, and didn't mind sacrificing a little profit.
However, Mixed Sea Fish was not cheap, and in order to raise healthy fish, it was necessary to purchase them, which in itself was a considerable investment. With the lake's fish yet to yield profits, hiring several people specifically to feed the fish would simply be too costly.