The most important thing in getting fish is selecting them at the fish store. This is important because many fish stores have shipped in fish from different places meaning they may have caught the fish in different ways. One way they could have caught them is by cyaniding them. Many fish die in route when being shipped to your fish store. Most of them die because they are under stress and get diseased or they die from starvation. They don't feed the fish because it can pollute the water and cause more fish to die, but the fish can live for a while without food its just when some are caught they didn't have any food in them at the time. Another way that fish are caught is by net. This is a healthier choice. When selecting your fish at your store you will see some fish checking out the tank being more energetic than others, those are the fish you want to choose. The fish laying on the bottom dead or sulking in the corner are obviously the bad ones. Also check to see if any diseases are on the fish so that you aren't bringing anything bad to your tank at home and that you have a healthy fish. There is one more way that fish are brought in to the store which is tank bread fish. These fish are probably more healthy than the net caught fish because they aren't put under stress when being transferred. Check for any redness on the fish in the tank with the fish that you want. If any one of the fish has redness to it than that probably means all the other fish have it or they are weak.

The use of cyanide                  Net Caught Fish

Source: The Marine Aquarium Problem Solver, Tetra Press, Nick Dalkin, 1996.