I have a 10 gallon fish tank that holds water with lid $15 and two Fluval 203 canister filters rated for a 75 gallon tank (best for 20 or 30 gallon tank as the rating is always optimistic). If you've never used canister filters these are great but they were only used for a year and then stored for about ten, so they probably need new orings (available for a couple bucks - ebay, amazon, etc.), new tubes, etc. Great budget way to get canisters if you don't mind doing some legwork. $30 for both.