I have a 3 gallon aquarium with an under-gravel filter that I would like to use in the future but I'm very new to aquatic pets. I am just trying to look at some options, I probably wouldn't actually get anything for quite a few months. Anyways, I do not want fish, since 3 gallons doesn't seem like enough for one. I was wondering if there are other aquatic pets that would be good for a beginner? Would a dwarf frog, or some type of shrimp be something I could look into more?