sorry but for saltwater small is difficult and cheap is impossible. i would invest in at LEAST a 30 gallon tank. at wal-mart you can get a complete 55 gallon tank kit for $160 which is a pretty damn good deal. if you think that's too expensive then throw the idea of ever having a marine aquarium out the window. the smaller the tank, the more difficult it is to maintain good water quality. due to space constraints, the first saltwater tank i ever had was a 10 gallon and it was the closest thing to hell you could experience