The bigger the tank, the easier it is to care for. A larger volume of water helps minimize the effect of temperature changes, pH swings, and the biological toxins that come from decaying plant and fish wastes. With toxins more widely dispersed in the water, your filters have more time to do their job, while your fish stay healthier. All of this means that beginning aquarium hobbyists don't have so much to fear from common early mistakes.

Also remember that small fish are generally more active than bigger fish, and are much happier with more room to swim around in, so don't get a small tank just because you like small fish!

In my opinion, the best size to get you started is a standard 40 or 55 gallon rectangular tank. These are easy to find, have lots of standard accessories, are relatively inexpensive, and they're easy to take care of. It doesn't take too long to change the water or do other standard maintenance, all parts of the tank are easy to reach, and you're less likely to have problems with algae growth than in a smaller, narrower tank.

Do yourself a few favors when looking at tanks to buy. Start with glass, because acrylic has its own tricky issues to master. Check the glass or packaging for a safety symbol, certifying the strength of the silicone caulking used to hold the panes of glass together. Also be sure to get a snug-fitting cover that's easy to clean - you'll need that to keep both feisty fish and evaporating water in the tank, and it's inevitably going to get filmed or crusty over time.

Buy a stand that's sufficient to support your tank's weight - remember that a 40 gallon tank can weigh up to five hundred pounds when it's full of water and gravel! Choose the location of your tank carefully, to make sure the floor is level and strong and, that direct sunlight doesn't fall on the tank during certain parts of day (this will throw your temperature maintenance off).

Set up the stand, and do anything you need to in order to make sure it's absolutely level - anything out of kilter will put pressure on your tank's glass or joints, and they WILL give eventually. Not a pretty picture!

Speaking of which, most modern fish tanks are never going to leak, break, or fall, but accidents do happen, and it wouldn't hurt to add a rider on your homeowner's or renter's insurance to cover potential water damage to your carpet or floorboards.