For a while now i've wanted to make a temperate saltwater aquarium from animals collected from a nearby beach. I then decided to make it into my science fair project by testing whether tides in a tide pool aquarium affected the fish in any way. But, you see, I am not only a newbie of temperate aquariums, but i've never had a saltwater aquarium before. I have been researching of course, and I kind of understand the basics of it but I would like a few tips. To attempt to simulate tides in the home aquaria, I will buy two 20 gallon aquariums, each with a power head on either side of the tank, along with live sand from a local beach and some tide pool invertibrates and fish. One of the tanks will have a pump that will drain the water to about half-way for six hours and fill it back up for six hours. So, my questions are these. Is a protein skimmer necessary? As it would be difficult for it to get down to the water while the "tide is out". What other filtration options do i have? Also, has anyone else tried to simulate the tides in an aquarium before? If you have any opinions on the project I would also love to hear them. Thanks!