Many organisms are lost due to inadequate, improper acclimatizing. Collectors, distributors, trans-shippers, wholesalers, retailers and hobbyists suffer most losses when receiving new livestock.

When placing fishes into a new environment there arises the possibility of physical, chemical, biological and social shock.

This article shows how to avoid these stresses altogether, or reduce stress after it has occurred.

There are a myriad of acclimation techniques; depending on the stocks genetic and developmental history and conditions at shipping, these are all to some degree appropriate and successful. However, many losses can be avoided or reduced with the information provided here.

An Overview of Fish Stressors:

Physical: 

To many fishes, even a small change in temperature over a short time is detrimental; thus attempts are made to equilibrate the temperatures in the new and old environs. Often this is done by floating the plastic shipping bags the fishes are transported in the aquarium. This process should continue for 10-20 or more minutes, depending on the amount of water shipped, the temperature difference, and the apparent strain the stock is undergoing. It's often a good idea to monitor the temperature in both environments. Opening the floating bag is not a good idea as the concentration gradient of oxygen may be higher if left sealed and an open bag usually reduces surface area and therefore gas exchange. Keep this in mind and maintain some surface area in the bag and/or add a mechanical aerator (an airstone) while adjusting for temperature.

It is also important that the aquarium lights be turned off during this time; especially incandescent bulbs, as they will heat the water in the bags too much, too soon. This results in decreasing gas solubility in the bag, increasing metabolic rate, frightening the fish, and generally cooking the fish. Many tropical marine fishes are intolerant of sudden or wide temperature range or photo-shock.

Be aware that thermally-shocked fishes may appear and behave "normal" on arrival and placement; only to die mysteriously within a few days. The biochemical and physical damage resulting from thermal shock often catches up later.

There is a school of thought that discounts the advantages of mediating temperature affects and admittedly if there is a time constraint and if the new fishes are under a lost of stress, they are often better off being introduced immediately. This is much more preferable if the water they are being moved into is warmer than the transported water. In general, cold water shock causes a great deal more harm than warm water shock.

Finally, regarding an "old-wive's tale" about the detrimental effects of floating polyethylene bags. In the latter 1960's there circulated a myth that this practice (THE AQUARIUM, magazine, June 1968, Vol. 1 no. 8 series II) would kill fish. This is hogwash.

Chemical: 

Usually, water will vary chemically from source to source. Sometimes the successful introduction of new fishes into a tank will largely depend on the chemical composition of the water involved.

It's often a good idea to try reducing some of the chemical shock by mixing water from your system with the shipping water on arrival or after floating. Do not put the shipping water into your established system! Especially in marine systems, the risk of introduction of chemical pollutants and undesirable organisms is not worth it. However, there are two scenarios in which adding shipping water may be beneficial: 1) When the receiving set-up has not been properly conditioned and 2) When "wild" stock chemical conditions are so different that even biologically polluted shipping water is better mixed in than all new "clean".

There are numerous techniques ranging from ingenious drip systems to simply adding a portion of new water to the shipping bag a few times every few minutes, to floating traps to....(see Jim Mortensen's June 1987 FAMA "If I Had Only Known"). Our most appropriate and successful method is detailed below.

Biological:

 There are three major components to a fishes health:

A) It's initial condition, B) The suitability of it's environment and C) The presence and virulence of infectious organisms (for a more complete discussion see A Livestock Treatment System; Bob Fenner & Dave Huie, Freshwater and Marine Aquarium, January 1988).

A) When you acquire fishes, make sure they are in good health. Buy from reputable sources. If you can, make a thorough inspection of their facilities. Are the fish being well fed? Are the plants well maintained? Is the staff knowledgeable and interested?

B) Most people's aquaria are ecological messes. Always check for the requirements and compatibility of the organisms in your care. You determine their world. What conditions have they been raised and kept in recently? This may be vastly different if you're dealing with cultured versus wild stocks. When possible, deal with a "local" source (see Buying and Trading Local Livestock, by Bob Fenner and Rob Lawracy, Pets Supplies & Marketing, April, 1987). For a lucid argument for a return to adequate acclimation, quarantine and conditioning at the wholesale level see the same periodical's May 87 piece, Detailing your Livestock Losses.

C) For most people it's hard to determine when you're adding undesirable micro-organisms. Keep your sights set on providing an optimized environment and follow the suggested acclimation process to avoid trouble. Remember: never add to a tank in which there is already a problem.

Social: 

It's often important which order the fishes are introduced, in what number, of what size, sex and type.

For example, many cichlids are easily crowded or under crowded

but not in-between. Among potentially aggressive tankmates it's best to provide either adequate hiding spaces or separate the

newcomers for a while with a divider or breeding trap. Often, a more aggressive fish introduced after its' fellows will behave complacently.

The sex ratio is important with many fishes; as with several livebearers. Small schooling fishes (many characoids, rasboras, Danios, barbs, etc.) should be kept in small odd-numbered schools.

Sometimes, if the fishes grow up together, they get along well even though in a natural environment one would prey upon the other. Always allow for some individual variation in temperament.

If there are ornaments or decorations in the aquarium, moving them at the time of new introductions is often advisable to confuse territories and disrupt agonistic behavior in the tank.

Our Method of Acclimation: 

After and while adjusting for temperature differences by floating or slowly adding water from the system to the shipping water, we net out or pour the mixed water through a soft net, and dip the fish in a prepared bath. The dip bath is the same for both fresh and salt water; we prepare freshwater from the system in a bucket (for salt water with the pH buffered upward with bicarbonate) with an ounce of 37% food grade formaldehyde per five gallons of dip and lower the net with the fishes in it into the bath. Depending on the type of species (short dips for small South American Tetras) and size and condition, this ranges from a few moments to a few minutes for salt water fish not exhibiting discomfort. Fishes thus acclimated and "dipped" are placed via net into their tank.

The mixed shipping water is then dumped through a "portable drain" consisting of a bucket with a thru-hull fitted through the bottom and connected with a threaded adaptor to a garden hose which empties to a drain.

Illus.

Admittedly, if the fishes are in good shape and the new environment not too unsuitable, you could throw them into their new homes with little ill effect. With attention to proper acclimatization, you will minimize your losses. Remember, prepare your holding system ahead of time. Hold off feeding for 24 hours after their arrival of your new livestock. Always condition and quarantine your fish before moving them again. Pay attention to these details and you will be rewarded with happy, healthy new additions to your tank.