Acclimating Saltwater Fish

Acclimating Saltwater Fish

Shipping is one of the most stressful things your fish will encounter. As a result, it is essential to properly acclimate them to your saltwater tank. Here’s how.

Marine animals are hardy, but shipping is one of the more stressful aspects of the hobby for them. As a result, they need to be acclimated properly to insure their health and well-being. This article discusses acclimatization procedures for marine fish. While not discussed here, it is recommended that all new marine fish be quarantined before being added to your display tank.

Temperature and Water Chemistry

Temperature and water chemistry (especially salinity and pH) are the critical factors when acclimating a new fish. The salinity and pH of the holding tank from which your fish came are probably different than the salinity and pH in your tank. The temperature in the bag has probably shifted during travel and is almost certainly different than the temperature in your aquarium. Finally, the water in which the fish was shipped will be of poor to very poor quality if the time in the bag exceeded more than several hours. Given all these differences between the shipping water and your aquarium, it’s easy to see how dumping the new fish directly into the tank without any sort of acclimatization would be a tremendous shock.

Float the Bag

The goal of acclimatization is to slowly familiarize your new fish to your system’s water. First float the bag (without opening it!) in your tank or sump for 15-30 minutes to allow the temperature in the bag to warm or cool to the temperature of your tank. Usually the fish was double-bagged, and it is a good idea to remove the outer bag before placing the inner bag in the tank. The reason for this is two-fold: 1) It provides less insulation and therefore the water acclimates more quickly, and 2) The outer bag may have come in contact with various substances you would prefer to not introduce to your tank.

Transfer Fish to Holding Container

Once the shipping water and aquarium water temperatures have equalized, remove the bag from the tank. Carefully open the top of the bag with scissors, and pour the contents of the bag into a holding container such as the Styrofoam box in which the animals were shipped (never mix shipping water unless you know the individual fish were housed in the same system water at the dealer’s).

Start the Drip

The best way to proceed is to drip acclimate your animals. Drip acclimatization is exactly what it sounds like. Over the course of an hour or more, you drip aquarium water into the holding container with the new fish and the shipping water. Setting up the drip is accomplished by using a piece of plastic tubing or “drip line” long enough to reach from the tank to the holding container. By tying two overhand knots in the tubing, you control the drip rate (the tighter the knots, the slower the drip). Create a siphon (by sucking on the end of the tube) to drain water from your tank into the holding container. Adjust the drip rate to 2-4 drips per second.

Repeat two or Three Times

Once the water volume in the holding container doubles, remove half of it, and repeat the process. Most fish will be ready to introduce to your tank after two complete cycles, although a third cycle certainly won’t hurt. Some aquarists like to test the water in the holding chamber and compare it to the water in the aquarium after the second cycle is complete. If you choose to do this, test for pH and salinity. If the numbers are way off, repeat a third cycle of drip acclimatization. Net the fish and add it to your tank.


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