My sister recently gifted me a 5 gallon fish tank that she previously had a beta fish in. Can I make a saltwater aquarium out of it? Do I need a special filter? What would be the best small species to put into the tank? Sea Urchins? How many could I theoretically fit in there, at one time? If not, what else could I put in there?
![season 6 episode 20 GIF by SpongeBob SquarePants season 6 episode 20 GIF by SpongeBob SquarePants](/proxy.php?image=https%3A%2F%2Fmedia2.giphy.com%2Fmedia%2F3o6wO6MtSaxC0fEJna%2F200.gif&hash=1398ebfa9573f9fddbfddbcbf5ad6827)