So... What does science have to do with keeping an aquarium?!
Here is a teeny, tiny illustration of this phenomenon:
First of all, an aquarium is an ecosystem. Period. Accepting this is absolutely a key to success- if you cannot think of the aquarium or "tank" as a small slice of a wild counterpart (ocean, swamp, river, etc.), you're going to fail over and over.
Aquariums are biological recreations of the real world.
Sometimes aquarists accidentally accept this fact. They may not recognize the hobby as "science" or that utilizing science will help them succeed; however, interestingly they actually use the scientific method of falsification in order to obtain success- another form of science in the hobby! Simply put, falsification is hypothesis testing: You make a prediction and if it fails, you know that's not right and you alter your prediction and try something else. Eventually you get a billion and one ways of doing something wrong and you forge a tiny little path into success. If aquarists stick to falsification long enough (have enough cash to blow, are stubborn, etc.), they eventually "accept" the ecosystem phenomena, whether they know it or not.
The hobby, accepted as science or not, utilizes it to just keep fish alive in an aquarium.
Other times, repetitive failure ends in quitting the hobby. And, of course, it's not this simple... understanding the hobby as science won't immediately make you succeed at keeping fish in a tank, but I bet it will get you there faster. Part of the hobby is figuring it out, taking chances, doing something crazy and seeing how it works. Failure keeps it challenging.
As I said, the hobby uses science just to keep fish alive in an aquarium. Another important and major science-understanding obstacle of keeping an aquarium is what aquarists call, "The Cycle". This concept may strike fear into a newbie- there are a lot of big, strange words. In the end, this cycle is the core of keeping aquatic animals alive in captive environments. The concept is important and its utilization essential.