So I am making a pond filter out of an old cat litter box. Problem is I tried to put the tubing through and seal it up with aquarium sealant but it is not working. The tubing moves too much and is easy to bump and I think that is creating bubbles and holes. Not too mention I don't think Aquarium Sealant likes plastic. The top hole now has some hose adapter pieces and a hose washer in between the box and the nut part of the adapter. I think I may go tomorrow and see if I can find a version of this for the smaller bottom hole, but I am not sure this is a possibility. Tonight I got some more hose washers, and some "thread seal tape." I am not sure if this is the same stuff as plummers tape like I thought. Is this or plummers tape safe to use? And is there any other suggestions to what I should do to make sure this is watertight?