#2 The Setup:

A Location) Decide carefully where you are going to put your tank. It is going to be HEAVY, you can't just move it around. Figure on about 8 pounds per gallon. While water is a bit less, remember, you have gravel, ornaments (all heavier than water or they wouldn't sink), a top, lights, filters hanging on, etc. This would make an average 55 gallon tank 440 pounds. A stand to hold this might weigh a couple of pounds itself. To move this, you will need to drain it, and that upsets fish (i.e., some will die). They don't like changes in environments. Make sure the floor is strong enough. Make sure you can reach all around the tank to clean it (remember, cleaning seems like nothing at first when it is new, but remember it is an ongoing affair). Make sure you can get something that falls behind it. Make sure the occasional spill (it DOES happen!) will not cause damage. Do your best to keep it out of direct window light (a tank in front of a window will grow algae where the sun hits it).

B Filtration) There are 3 basic types of filtration. 2 out of three will work, 3 out of 3 is ideal. First is mechanical. This filters out the physical particles in your tank. This is more for us, than your fish. They don't mind 'dirty' water, if it had the correct composition. Many ponds / lakes you see these fish in naturally do not have crystal clear water. However, much of the 'dirt' that generates in the tank will also contribute to bad water quality. Decaying food, dead fish, fish waste, all wreak havoc on water quality. Plus, even if it were just for us, there would be no sense in keeping fish if you couldn't see them! Second is biological. Fish produce waste that is toxic to them. "Bad" bacteria. Fortunately, there is such as thing as "Good" bacteria, that lives by eating bad bacteria. It takes a while to grow a colony of good bacteria, and they won't grow if they don't have any bad bacteria to 'eat'. This good bacteria lives on solid objects, and thrive with water flow (constantly being brought dinner!). Most mechanical filters have some sort of media that serves as a host for good bacteria. Unfortunately, most people 'wash' these, or replace them during filter cleaning, in effect, killing all that good bacteria. An even better form of a biological filter (best 'in addition to') is an under gavel filter. What these do is sit on the bottom of the tank, and keep the gravel elevated just a small bit. Then, either by simple air bubbles (for very small tanks), or a power head, they pull water from under this space, making water flow through all the gravel. This creates a very large field for the good bacteria to grow and thrive. Personally, I prefer the power heads that will 'push' water, rather than pull, because it will keep your gravel much much cleaner. When it is pulling, it is sucking in any dirt material into the substrate. When it pushes, it is providing the same 'flow' across the gravel, but actually pushing the dirt and debris out of the gravel, and up into the water, to be grabbed by the mechanical filter. (one step beyond this is a wet/dry filter, but again, it is normally used in a  more advanced system than a typical beginner setup). Finally, and the most likely overlooked in a beginners system, is a UV filter. While it is overkill in a small tank, and relatively expensive, it is a must for anywhere you are planning to put fish that you don't want to lose. UV sterilizers use ultraviolet light to kill bacteria in your system. It will kill good and bad, and more importantly, disease causing bacteria. You save money on lost fish, medication, clarifiers, etc. In a small tank, these losses are cheaper than a UV, but once you get to at least a 55 gallon, you will save money with the UV. It also kills algae, which is a problem in most all tanks. You will not experience an algae bloom with the UV, and if you have one, it will clear it. It requires very little maintenance, and is extremely effective.

B2 Filtration sizing) DOUBLE IT! Plain and simple, go with more / larger than what the manufacturer says. It normally doesn't cost much more to go one size up, but just like the UV, will save you money and headaches in the long run. Now, if you have all the 3 stages of filtration mentioned above, each one does not have to be doubled. But, even with all three, you never want any of them to go under the recommendation as if it were the only one.

C Aeration) Proper aeration is critical to the water chemistry of your tank. Contrary to most beginners beliefs, it has nothing to do with providing air to your fish. (well, almost nothing) It's chief purpose is to agitate the surface, and let the 'bad' chemicals in the water out. The surface tension of water is just enough to lock all sorts of bad chemicals (that fish produce) within the tank. Bubbles happily break this surface tension, and let the stuff out. Most power heads (for your under gravel filter) have a spot for an air tube, so while it is doing the wonderful job of biological filtration that your fish so desperately need, it is also capable of aerating your tank, to a huge degree! A bargain, do not go without!