I found that once the algae fish is noticed in the pond, ANYONE adept or over can go fishing and bring the fish over to the ocean ... if they can see them, they can catch them ... and the more people you have bringing over fish to the ocean, the shorter the time is to solve the problem :). As far as I know, and I've been playing quite a while, the algae problem never seems to crop up again even if all the farmers are fishing their little hands off constantly between crop plantings.