Even with all of the necessary precautions in place (e.g. mesh screens or glass lids), wandering fish can find their way into the most random of places in your aquarium. Fish can squeeze through intake strainers and mesh, travel through plumbing, and even hop baffles to take up residence in various parts of the sump or overflow box. There isn’t much you can do to keep the fish in the proper display portion of the aquarium, so it’s best to constantly check all of those random places for fish and other aquarium livestock. You might need to use a small, and we mean really small, net to catch your livestock out of those tight places.