Well, my suggestion is to return the Rosy Barb, explain why to the store, and select something suitable for the tank.
There are a couple reasons why this is not a good fish in this tank. First, fish size; 3 inches is minimum, and some sources say up to 6 inches. There is insufficient space in a 24-inch tank (regardless of the depth or volume) for a group of such fish. Then there is the swimming issue. These fish need space to swim down the tank. This is an essential aspect of their evolution, and it is being denied to them.
Fish that are placed in tanks that are small (to the fish) frequently develop health problems due to stress from sheer frustration. They always have a shorter lifespan.
Please follow the guidelines in the profiles; they are minimums recommended by biologists and ichthyologists who know the fish species better than any of us.
Edit: I just came across another (newer) thread on the same topic so I have merged it into the older thread. It is better not to start a new thread on the same issue because we all need to see the whole story in order to be of assistance.
Last edited by Byron; 11-24-2012 at 01:11 PM..