well, I mostly know about goldfish and from what youve described, I dont suggest getting one. they are big, and REALLY messy fish, and one goldfish needs at least 10 gallons, 20 being ideal, and of course, the bigger the better. not only will the fish be happier & healthier in more water, they will also have more room to grow (most goldfish are at least 6-8 inches at full size), AND the bigger the tank, the less often it needs to be cleaned! a 10 gallon needs to be cleaned every week or 2, a 30, every month, a 50 every 2-3 months, etc. overstocked tanks are a LOT of work, and if they arent kept clean the fish can get sick very easily. a lot of people think goldfish are easy fish, but they really arent. and I dont think most people realize that goldfish can actually live up to 10 years or more when cared for properly.

if you want a tank smaller than 10 gallons Id suggest a betta or, as others have suggested, some of the small tropical schooling fish. if you ask me, tanks/bowls smaller than 5 gallons shouldnt even be made. but thats just my opinion. I know some fish do fine in small spaces, I just think why not just add a few more gallons?? (although, I also think a 30 gallon tank is small. lol) there are some great 5 gallon tank setups that you can get at petsmart and petco that have a filter & light. (http://www.petsmart.com/fish/shoppin...%5F28003.shtml) a filter will make your life a LOT easier! less cleaning, plus if you have a power filter you dont need an air stone/bubble maker.

and as for how many fish per how many gallons, it all depends on what kind of fish!

petsmart's website is a great resource for fish care info and they have a section about fish breeds and how to care for each kind. Ive always found petsmart's website to have very accurate and reliable information.