i started of with a 50 gallon tank and now want a bigger one i never had any problems with it. the size of tank also goes on what you want to put in it small shaoling fish or bigger the smaller the fish the more you can put in the bigger the less it all depends on what kind of fish that you want to keep in it. my tank is a mixed comunity tropical and has 35 different sized fish my 20 has 16 guppies that are swiming and breeding so it all depends on what you want to keep
I can just see my trying to fit a 7 foot wide tank in my 4x6 foot bedroom. 
not to mention my bed and everything else... 
Sorry, but this is wrong. Like you said, you can clean your 3 gallon easily, but with a larger tank, you don't need to clean as often. I have a 55 that hasn't had a water change in over a year. In the summer there isn't much evaporation because of the humidity out, so I change 5 to 10 gallons a once a month, maybe a little more. In the winter with dry air it looses about 10 gallons a month so I just add about 5 gallons every other week without having to drain any. I use a siphon hose and vacuum the bottom when it gets bad, that's maybe every other month, sometimes less because if you have good filters and a bubbler in the right spot, you can have a current in the tank that keep stuff from settling then your filter grabs it all and you don't have to manually clean.
I know this is a really old post, but I completely disagree. A larger tank lets the aquarist react to problems a little slower. Remember "Dillution is the solution to pollution!". The Bigger the better, especially when you're dealing with water issues.I think a 10 gallon is a good size for a beginner. In a way the bigger the tank the more work
I see this is a bit late to respond to but I have been using sand for a substrate for the last two years and I doubt that I will ever change. The look it gives my tank is beautiful. Needless to say I also found this a bit harder to vacuum. After quite a bit of trial and error I found a way of doing this without losing so much of my sand. Now, I dont know how this would have worked in the past on some of my smaller tanks, but at this point in my addiction I am maintaning a 300 gallon tank that occupies about a quarter of my bedroom. This in itself may have created a situation more closely resembling the upkeep your local fish store deals with on a regular basis so this might be out of the question for some people because of what it entails. My tank is fairly close to the window in my room so I run a 25 foot length of inch and a quarter smoothbore vacuum hose I picked up at a pool supply store where i worked at the time. I also picked up a plastic valve to make establishing the syphon much easier. i run the hose out into the yard and into a 7 or 8 gallon bucket and once I get the syphon going I vacuum from about an inch and a half off of the sand and pick up very little sand inspite of the amount of suction i get with this method. when I added polished stones for contrast I put a 6 inch wide household vacuum cleaner head on it with a little brush in it that prevents me from sucking up the stones. I lose about 30 to 40 gallons of water and about a pound of sand which stays at the bottom of my bucket and when I'm finished I just pour it back into the tank before I add my chemicals and refill . I know this must sound like a lot of work but all my sloshing around and water spillage is outside on the grass and it takes about 15 to 20 minutes to finish my upkeep this way.
WOIEJFLABest tank shapes common in the USA IMO: (IN order of best to worst... still all good). These have the best surface area in each class. Tanks are one of the cheepest parts of setting up a system. You will spend way more money on food, gravel, thermometers, pumps, digital camera, FISH, and other things. Get the right shape!!! and get the largest thing you can fit into the room (with respect of going over the 75g mark). The only tank you are really getting a deal on is the 10g for cost per gallon, so just get the largest tank you can… If you answer oo but that is too much. get a piggy bank. If you stock good levels of fish (2 “ per gallon) on the larger systems you can start off with pretty cheep filtration.
Fresh Water Best tanks
180 Gallon 72 1/2 x 24 1/2 x 25 5/8
100 Gallon 72 1/2 x 18 1/2 x 19 3/8
120 Gallon 48 1/2 x 24 1/4 x 25 1/2
75 Gallon 48 1/2 x 18 1/2 x 21 3/8
Smallest recomended 40 breeder though low in volume does have nice surface area.
40 Breeder36 3/16 x 18 1/4 x 16 15/16
30 breeder good too but less common I believe.
20 Long 30 1/4 x 12 1/2 x 12 ¾
…………………
I highly suggest getting 2 overflows in any new tank. Even if you are not doing salt water you can put pre-filter sponges in them for your cans or HOB inlets. And, they pull off surface scum. This cost may be more than its worth for many.
………………………….
I don't suggest under a 20L for anyone new to the hobby 40 breeder or larger would be best (but not as cheep as the 20L
10g are inexpensive and great for sick tanks, but too small to be considered "easy" care.
IF you HAVE to go smaller the 15g normal Long? is ok as well as the 10g, but the 20 High is a waste of space IMO.
55g are not bad tanks... but the price difference is worth having the 75 for surface area and aqua-scaping.
If you are unsure of your floor's strength. stick with a 75 or less. (If your floor can’t handle 1,000 lb spread over 4 feet YOU NEED TO CONDEM THE PREMISIS).
PS Any one know how much pressure the ball of my fat 200 lb man foot puts on the floor boards when I jump up and down?
Any other shapes are inferior
