I have a yellow watchmen goby and in the last week he has managed to make his way into the overflow box down the piping and into the sump. The first time he was in the skimmer and today he was under the bio ball basket. How can I stop him from going into the over flow box with out stoping my water flow? Any suggestions? I was thinking a acrylic piece with smaller holes but I am not sure if this is a good Idea..... Also I just got a sally light foot crab hes about 2.5 in from leg to leg he wont go after my fish will he? my clowns are about 1in and 1.5in and my lawnmower blenny is about 3in long?