I forgot to mention the KEY!!!
You will need to punch or drill small holes on the bottom of the rubbermaid cup I did 3 rows of about 10 all around the bottom and a few on the very underside of the cup too!!
water is pulled in from the holes by the pump,then expelled back into the tank from there.
getting tubing that'll fit snug inside the bottle opening on it's lid is also very important.
You could do this same method with smaller tubing,and any cleaned out Soda container (2liter),or even one of those funny costco style rectangular milk jugs,and larger tubing