Now I know it's not the best thing to keep fish in a tank under 10 gallons but college students and some people just have space restrictions. Don't worry though you can still keep fish. Some Fish that is. First proper filter: DON'T GET UNDERGRAVEL FILTERS!!! These things don't work well unless you have power heads hooked up to them. The best small tank filter is a small in tank or out tank power filter rater for 10 gallon tanks. BTW This is for tanks smaller than 10 Gallons. Second If you don't have goldfish which you could though I don't recommend it make sure you have a heater. Now I recommend a heater that you can set to a specific temp. They cost a bit more but are well worth it because most heaters can over heat your tank. Remember quality is a must in this hobby. Next a thermometer, you need to set your temp according to your fish, some like it warmer others on the cool side. You also will need a air pump and air stone. Honestly you fish will be healthier with it. If your a beginner fake plants are for you. Make sure you provide adequate cover for your fish. Rock caves are great too. On to Gravel: You should have 1-1.5inches of gravel no more. Pick a color any color. I like black myself. Kay now you have your set up. Time to cycle. I'm sure most of you know it will tank about a month for your tank to be ready for you fish to go in. On to what Fish can I have? Well believe it or not a lot of different set ups will work. I'm going to throw out a list of fish best suited for a smaller tank. These fish should really be in at least a 5 gallon. Guppies(Get males unless you want a bunch of guppies one morning when you get up)Minnows/Danio's. While there's some debate on if they do well and are happy in a small tank it's been my finding they do fine. Tetras - The smaller ones like Neons,glowlights, Black neons...You get the picture. Betta's of course however tank mates are limited. Cory Catfish. Though it's recommended a group and school a pair will do fine in most set ups just make sure you get them small. Dwarf Gourami's, a neat little fish but remember you can't overstock, when you have a fish as big as a gourami you are limited. Now onto fish that I've seen do great in small set up though it's not recommended. Cichlids....did I just say cichlids? Yes I did. My brother has had a single Bolivian Ram with 2 peppered corys in a 6 gallon systeam for 2 years going on three. Dwarf cichlids as they are called can do fine in here but some times you will get a bully and if you do keep a ram, only ONE and maybe a peaceful bottom dweller. Like I said I don't recmomend it but I've seen it work. One last thing to remember is don't get a fish that gets bigger than 2-3inches. You will stunt them.