Danios aren't easy to sell; they're common to any LFS; no one is going to want to pay shipping for them. Like I said, it's unwise to have a fish that you just plan to get rid of later. What if something comes up? A good, compatible tank mate that will do excellent in your tank and grow large enough are dojo loaches, you can get 3. They will do better if you have sand or small gravel though.