When you buy fish to put it in a tank, there are some basics to be followed to avoid losing fish as they are very sensitive to subtle changes in their environment and water conditions. Let's guide you by giving a few ideas on how to further avoid this.

• Bringing new fish home from a store is always stressful to them, and some fish are especially sensitive to any sudden changes, such as Ram's, Clown Loaches and Neon’s. Therefore while selecting one choose the brightest colored, smartest swimming fish as it will stand a much better chance of surviving the stress of moving.
  
  
• It is often said that the best water parameters for a fish are the ones it's in right now and they do not like sudden changes. A change of more than 0.2 in pH or 2oC in temperature in a period of less than 8 hours is stressful, and can be fatal. Ask the shop keeper at which level he maintains these parameters in the tank you're choosing the fish from.
  
  
• If possible, check the fish's appetite too.
  
  
• For transporting the fish to home make sure, the fish has a reasonable amount of water in the bag. Always transport the fish in the dark, it calms them down. If you're going to take more than a couple of hours to get home or if there are several fish in the same bag, ask the shopkeeper to put oxygen in it.
  
  
• Before releasing the fish into your tank, float the bag for at least 10 min, during which you should slowly add your tank water to the one in the bag. This helps adjust the pH and temperature of both waters. After this, throw the water in the bag away and release the new fish into the tank.
  
  
• If you're worried that some of the older fish might attack the newcomers, turn off the lights and/or throw some food in the tank to distract them until the new fish can find a suitable hiding place.