As with tropical freshwater fish, marine fish need to be transported with care and your retailer should package the fish appropriately. If you are travelling for more than 30 minutes let your retailer know before they catch your fish and they may make special provisions. Marine fish will need a little extra care during acclimation so it is important to get these steps right for a stress-free introduction.
Acclimating the fishThere are many properties of water chemistry that will be different in your aquarium to the water from which your new fish has come, and it will take your fish a little time to get used to these changes. The two properties that will have an immediate stress or shock inducing effect are temperature and salinity so these are the areas that need to be focussed on. When you get home with your fish the first thing to do is switch off the lights on your tank – a sudden change from the darkness of a bag or box to the glare of aquarium lights can be very damaging. Your fish can then be floated on the aquariums surface, still with the bags sealed to prevent the fish jumping out. Leaving the fish like this for 5 minutes will allow enough temperature equalisation to prevent serious shock in the event of an escape, so after this period the bags can be opened and the sides rolled down so that the bags are still floating but open. Over the next 20 minutes or so you should add a little tank water to the bag periodically, aiming to end up with about three times as much water in the bag as when you started. This process of slowly adding water will help to bring the salinity nearer to the level in your tank, and the fish can then be released into the tank.
Monitoring new fishOnce your new fish are introduced, it is best to leave the lights off for a few hours – this will both prevent stress to the new fish and also calm down the existing fish so they are not 'over-interested' in the new addition. Over the next week you should closely monitor your new fish to make sure it is settling in and that any existing fish are not causing it problems. Avoid any stressful activities such as tank cleaning or water changes during this settling period, and spread your feeding out into more frequent feeds, ensuring the new stock gets plenty of food.