Is it permissible to feed pork to fish in a farm, knowing that pork is forbidden for a Muslim?

Scholars are in consensus regarding the prohibition and impurity of pork. However, they differ on feeding impurities to animals:

- The Malikis and Shafi'is permitted feeding impure fodder to livestock. - The Hanafis prohibited benefiting from anything impure. - The Hanbalis permitted feeding impure substances to animals whose meat is not eaten, but they did not permit it for animals whose meat is eaten, except after confining them for three days.

One should avoid feeding fish impure substances to avoid controversy. If fish are fed impurities, they become jallalah (animals that feed on filth). They should then be fed pure food until their meat becomes wholesome, and it is disliked to eat them before that.