Would it be possible to harvest energy from fish?

Let’s say it could, because it probably could. Then look at the problem from a practical standpoint.

That goldfish survives for at least a day on some tiny flakes of food. That’s all the energy it takes in and so it can’t possibly generate more than what’s contained in those flakes.

Wouldn’t there be a more efficient way to capture that energy than strapping generators to millions of goldfish and solving the problems of how to transfer it?

You know those water fans? Well, instead of using batteries, they should totally use a hyper goldfish to produce energy. The only problem will be refilling water so the fish won’t die. Oh no!

We’ve overfished the oceans to the point where we may not have enough fish to eat. Fish energy doesn’t come from nowhere. You would have to balance the energy needed to grow the food for the fish and keep the tank clean so the fish wouldn’t die with the amount of energy the fish produces.

I think this guy has a better idea on how to grow and use fish.

We harvest energy from fish every time we eat them.

You would likely generate a similar amount of energy by burning the pinches of fish food rather than feeding them to the fish. The chemical potential energy of the food is much lower than that of gasoline or coal.

Plus, PETA would go berserk.