Proper acclimation of your new fish should be your goal. Why? Because the life of you finned friends depends on it. Depending on the source of your fish, the salinity could range anywhere from 1.016 to 1.026, in addition the pH in the bag is going to be significantly lower, more so if the fish has been in transport for several hours. Temperature differential is the most obvious and usually taken into account by most hobbyist. However the cause of many failed acclimation attempts is ammonia.
As the fish is transported, waste is released and therefore elevates the level of ammonia in the water. When coupled with the lower pH, the elevated ammonia isn’t as detrimental. However soon as you open the bag or expose the water to an open container beware! You might believe that your’re allowing the fish to ‘breathe’. Yes, but, you’re also allowing the pH to rise as the CO2 off-gasses, and consequently increasing the toxicity of the ammonia. And this is where things can go badly for you and your fish. Especially if you have a longer acclimation period due to large disparity in salinity, temp or pH.
Consequently, it’s a great idea to move your tank water parameters closer to your incoming fish’s water provided there’s no existing livestock. This method works well if utilizing a quarantine tank, since you won’t be affecting the environment of your main aquarium. If you are bypassing the quarantine process, which we highly recommend you do not, a bit of dechlorinator such as Seachem Prime is recommended. Add to the bad or acclimation container and protect your new fish from a silent killer.