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Related FAQs: Acclimation, Acclimation 2, Acclimation 3, Acclimating Marine Invertebrates, & FAQs on Acclimation: Rationale/Use, Tools/Gear, Chemicals, Methods, Controversies, Troubles/fixing, & Acclimating InvertebratesDips/Baths 1, Best Quarantine FAQs, Quarantine

Related Articles: Acclimation, Quarantine ppt., pt.s 1, 2, 3, 4, 5, 6, 7 by Bob Fenner, Dips/Baths, Quarantine, Quarantine of Corals and Invertebrates, Methylene Blue, Acclimating InvertebratesAcclimating Symbiotic Reef Invertebrates to Captive LightingQuarantine, Quarantine of Marine FishesCopper Use, Formalin, Formaldehyde Use,

/The Conscientious Marine Aquarist

Acclimating Marine Livestock for Home Hobbyists

(& See Article Below on Commercial/Guerilla Acclimation Techniques)

By Bob Fenner

 A "cut", doomed Chromis

Many saltwater organisms are lost simply due to inadequate or improper acclimatizing. Many folks not in the trade, don't realize that collectors, distributors, transhippers, wholesalers, retailers and even hobbyists suffer most of their losses in the process of receiving new livestock.

When placing newly-arrived fishes, invertebrates, algae, and live-rock into a new environment there arises the possibility of physical, chemical, biological, even social shock. This article shows how to avoid and otherwise ameliorate the effects of stress after it has occurred.

There is a wide range of possible acclimation techniques; depending mostly on the species at hand, its apparent health, and conditions at reception. The varying prevailing methods are to some degree appropriate depending on these criteria. Whichever protocol is chose though, know that many losses can be avoided or reduced with careful acclimation.

Sources of Trouble: An Overview of Livestock Stressors:


To many marine organisms, even a small change in temperature over a short time is detrimental; think how stable the oceans are thermally. Earnest attempts should be made to equilibrate the temperatures in the new and old environs. Often this is done by just floating plastic shipping bags the life is 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 bags is not a good idea as the concentration gradient of oxygen may be higher if left sealed (if the bags have been filled with concentrated oxygen) 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 should however be mentioned that there is a school of thought that discounts the advantages of mediating temperature affects and admittedly if there is a time constraint or if new specimens under duress, 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.

Do be aware that thermally-shocked fishes may appear and behave "normally" 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.

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

Lighting Concerns: 

It is also important that the aquarium lights be dimmed or turned off during acclimating time; especially bright sources like halides, 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 livestock, and generally cooking them. Many tropical marine fishes are intolerant of sudden or wide temperature range and/or photo-shock.

Chemical Concerns/Dangers: 

Usually, water will vary chemically from a source to your system, even if originally from the same brand of mix, set at a similar specific gravity. More often than not, the successful introduction of new livestock into a tank hinges on the relative chemical composition of the waters involved.

It can be a very good to disastrous idea to try reducing some of the chemical shock by mixing water from your system with shipping water after floating. Allow me to explain. Several "things" happen in an enclosed shipping bag as time ticks by... Even if "pure" oxygen (99+%) versus ambient (@21% by volume) oxygen is employed in sealing the bags, the alkaline reserve of the water gets nicked down bit by bit, and pH will start to drop, carbon dioxide increases in concentration as carbonic acid, decreasing pH further... ammonia from the livestock from excreted wastes, secretion from the gills and body increases, accumulates in concentration... This is enough of the picture we need to portray. Depending on how much of these changes in the water's make-up have occurred, you want to mix-waters or not. How to tell which is the case? For short trips from the dealer, let's say an hour or less, you're probably better off blending in the system's water to acclimate new stock. If you prefer, using a test kit for pH and ammonia will give you a window into whether to mix or not. With any detectable ammonia and any measurable difference in pH, do not mix waters. A rapid elevation in pH coupled with ammonia is extremely toxic to almost all aquatic life. Of course, just like grading school papers, "when in doubt, count it out". If you have a concern about whether it is better to blend a specimens shipping water with the system to acclimate it, don't. For long-range trips, and folks dealing with many or expensive animals, please read the next following article on Commercial Acclimating Techniques carefully.

Do not put the shipping or mixed water into your established system! 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"). The most appropriate and successful method I've seen is detailed below.

One Method of Acclimation:

After adjusting for temperature differences by floating then possibly slowly adding water from the system to the shipping water, net out the organism or pour it and the mixed water through a soft net, using a plastic bucket to support the net and to hold the mixed water. Move the "decanted" livestock to a separated system for quarantine. Isolating most all kinds of new marine life is extremely important, allowing the new stock to "rest up", grow more accustomed to captive conditions, foods... w/o being harassed by well-established tankmates... This time also grants you time to observe the newbies for signs of illness, perhaps to treat them for pathogenic disease, or to discover some "hitchhiking" pest that would be real trouble if introduced to your main display system.

If you don't have a quarantine system (yet...you will in time...), you are advised to perform a dip/bath procedure for most types/species of marine fishes. There are a few variations on a theme here... here I'll present a dip/bath for salt water that is a semi-standard used in the industry of pet-fishing. There are assuredly others. And yes, some folks never "dip" and have never had a disease problem. I want to make it crystal clear though... prophylactic dips/baths are of tremendous utility... to a huge extent ridding fishes of external parasites (Cryptocaryon, Amyloodinium and other protozoans, worms and crustaceans of various sorts).

We prepare freshwater from an ongoing system or dechloraminate tap in a bucket (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 Clownfishes and other livestock that lives in close association with, or is an invertebrate) and size and condition. Time ranges from a few seconds to a few minutes for salt water fishes not exhibiting discomfort. It is a very good idea to add mechanical aeration (a bubbler).

Fishes thus acclimated and "dipped" are placed via net into their tank, either the system, or preferably quarantine.

The mixed shipping water is always dumped to waste.

    Remember, prepare your holding system ahead of time. Generally it's best to hold off feeding for 24 hours after the arrival of your new livestock; and always condition and quarantine your livestock before moving them again. Pay attention to these details and you will be rewarded with happy, healthy new additions to your system.  

/The Conscientious Marine Aquarist 

Commercial (Ye Olde Guerilla) Marine Acclimation Methods

Please see:   Dips/Baths  for much more re chemical use...


By Bob Fenner


Re: Saltwater die off Thanks for the reply Bob. I will pass on the info to my customer. BTW, since using your medicated bath from the "Guerilla Acclimation Techniques" I've had a huge improvement in the health of fish coming into my store. You and the rest of the crew have done wonders for the aquatic community, and I know of many fish who would thank you as well if they could speak. :) Regards, James Foley Thunder Bay Aquascapes www.tbaquascapes.com <Ahh, thank you my friend. BobF>

What's your biggest source of enjoyment from keeping aquatics? Probably the livestock with the emphasis on live. As conscientious consumers of the living aquatic environment we are faced with moral/ethical questions of "rightness" in what we choose to do in our hobby. How much wear and tear on habitats, loss of vitality, life is acceptable and for what acceptable reasons? Let's think about this; we have discerned effects on the planet, we should be aware of what we're up to.

An inescapable fact of life is it's apparent antithesis: death. As difficult or unprofitable as it's discussion may be

the loss of aquatic life is equally inevitable. The magnitude of these losses at every level, collector, breeder, intermediary to end-user is very large; some reasonable estimates exceed ninety-plus percent... Some of these losses are unavoidable practically or economically. It is a fact that unlike amniotic mammals, the lower-vertebrates (fishes) undergo a great deal of development in free-living stages, with concomitant losses... and that pet-fishing in the business sense is an economic endeavor, done for profit. If cost were not a chief concern the trade would be very different indeed.

Where do most losses occur? At what point in the use of aquatic organisms is mortality greatest? You know where, and it's the same for all levels in the chain of production and distribution; at the transition of moving/acclimating/and stabilizing "new" livestock from one system to another.

Definition of Opportunity:

A search through the cited scientific and my semi-exhaustive pet-fish hobby and business pulp, bound and ephemeral materials turned up surprisingly little of real use on the important topic of acclimation. Why? Is acclimation of such small consequence? Decidedly not. I put it to you again, ask yourself, other aquarists, the dealers when and where do they lose most stock? Are acclimation methods "secret", "hocus-pocus" maneuvers that convey special status or abilities on wizards of wet-pets? No, it seems to me that most folks are just too embarrassed to admit their losses; or their lack of "coming to grips with the realization of their own limitations".

It is my desire here to:

1) Acknowledge the dimensions of mortality that occur consequent to poor, inadequate or inappropriate acclimation.

2) State that these large losses occur across the spectrum of collectors, breeders, consolidators/transhippers, wholesalers, retailers, hobbyists.

3) That much of this loss is avoidable and

4) Offer my "Standard Operating Procedures" for marine and freshwater acclimation.

This discussion is intended to provide stimulus, some guidance and insight for others to adapt/adopt, and a jump on/off point for the bridge between the scientific and hobbyist literature. We possess a great deal of empirical knowledge in the hobbyist realm; the scientific world is prophetically swarming with disparate, fragmented facts and for-the-most-part unusable high-tech (immunofluorescent, bio-chemical, micro-, ...) factual material. Pet-fish magazine articles are followed and indexed by citation services. Maybe the twain shall meet sooner.

Individual's with a small collection, adding one or two specimens from time to time should benefit from the following guidelines for large-scale mass processing and are referred to Steve Landino and I's piece in 1989's FAMA.

Acclimation in General: Preliminaries

If it isn't obvious, these opinions are just that, the syntheses of my experiences in this field through the last thirty years in the trade, twelve years of college and passionate involvement in the wonder and hobby which is aquatics. The following notions are intentionally generalized and therefore necessarily broad in scope and application.

It seems expedient to list some of the conditions and actions appurtenant to proper receiving of new livestock before diving into specific acclimating techniques:

1) Be Prepared: Aquaria, conditioned water, nets, tubs, and other necessary tools and materials clearly need to be on hand; including adequate personnel. If you have may bags and boxes, acclimation can take a few to many hours. The longer the livestock remain unpacked the greater stress and loss of vitality. Do you have separate quarantine facilities? What about protection of & from existing tankmates?

2) Be Programmed: Detail acclimation routines in writing and practice them accordingly. Post list(s) of what's to be done in order, label the receivers (tanks) ahead of time.

3) Be Systematic: Establish and adhere to a routine. Treat the livestock shipments in a replicable manner and keep track of your results (a small journal notebook works as well as a personal computer). Change your routines in a conscious, decided, one-variable-at-a-time manner.

4) Be Conscientious: Pick up and move your livestock from point to point without delay. Work steadily, under subdued lighting.

Salt-Water Acclimation Steps To Completion:

A) Boxes opened and bags quickly cut with dedicated scissors or knife.

B) The same types of kitty-litter trays are tilted on end and compatible fishes are gently poured, shipping water and all into the tub.

C) An airstone is added for mechanical aeration.

D) Treated (pH adjusted) holding system water is added either gradually ("dripped") or in increments every few minutes. And what is it treated with? The same PVP dechlorinator and Methylene blue (to add oxygen and slow ionic "leaking"), and one other addition:

An acid is added to temporarily ameliorate the difference between the shipping and holding conditions. I employ phosphoric acid usually. You can buy this as Aquarium Pharmaceutical's pH Down if you like; there are others. Some places utilize dilute hydrochloric, available in three molar concentrations as Muriatic acid from pool supplies outlets; I have seen CO2 gas used as well... What matters here is that we lower the pH down to somewhere to approximately that of the shipping water. This will require some initial testing and experimentation. Check the pH of the shipping water and determine about how many drops of your standard acid mix is required to drop the acclimation solution to about the same point. You'll want to do this with a few bags each consignment as conditions affecting pH will vary with each shipment.

The intent of this step is to reduce metabolite poisoning coupled with high/er pH (much more toxic) & drive off excess carbon dioxide through dilution and aeration.

E) Additives: I endorse the use of Methylene Blue universally... as being a great and safe addition to reduce stress (by screening light), aiding in oxygen transfer, and having mildly antimicrobial activity.

F) Transfer: A minimum of fifteen minutes, maximum of an hour or more may be required for the fishes to stabilize and reconstitute. We want the therapeutic chemicals added to the acclimation solution to have time to make their way into the new fishes.

Holding systems are divided into Fish and Non-fish, as your new/quarantine arrangement should be. On the vertebrate side of systems we used to continue to keep a titer of copper, chelated and free as a matter of general practice. Specific gravity was kept a little on the low side (1.021-1.023) except for Red Sea, some Indian Ocean, Clownfishes and other fishes that live in close association with invertebrates. These latter were often placed in the Non-fish holding and quarantine systems.

Non-fish (live rock, invert.s, algae) are of course kept in higher salinities without copper. Their initial handling is so diverse and specialized it merits separate discussion.

What Do These Acclimation Methods Do?

That is, what's the objective of all this rigmarole? First and foremost, overall to optimize the well-being of new livestock. To get them from their origination point, over the stress and damage from handling and shipping, to their final destination quickly, opening, inspecting, stabilizing, treating for damage, parasitic and infectious disease and "hardening" before further handling.


Rest assured I am more than acquainted with many of the other novel tools and techniques, and more toxic materials; the use of ozone, oxygen, peroxides, permanganates, malachite, and many others. These are not worthwhile in common use as being unnecessary and dangerous to livestock and their handlers.

I have been party to bumping off (some euphemism now!) a few some hundreds of thousands of aquatic organisms over the last thirty years in the business, science and hobby of aquatics. These materials and methods are the best that have globally worked for me and the applications I was involved with. You are welcome to comment, add your experience, or put them to your own profitable use. Whatever system you utilize for acclimation, approach it scientifically, record your observations, and share what you learn.

References/Further Info.

Blasiola, George C. 1991. Acclimating Marine Fish. Pet Age 12/91.

Bourdages, Howard, M.D.. 1992. The Acclimation of Marine Fishes. FAMA 2/92.

Fenner, R and Rob Lawracy. 1987. Choosing the Right Multi-tank System. PSM 4/87.

Fenner, Bob & Steve Landino. 1989. Acclimating Fishes. FAMA 8/89.

Fenner, R.. 1989. Improving Your Store With Central Filtration. Pet/Supplies/Marketing (PSM). 11/89.

Fenner, R. & Phil Farrell. 1990. An Inexpensive Aquatic Holding Facility. FAMA 1/90.

Fenner, Bob. 1991. Central Filtration Systems. FAMA 12/91.

Herwig, Nelson. 1979. Handbook of Drugs and Chemicals Used in the Treatment of Fish Diseases. Charles Thomas Publisher.

And Gratefully Acknowledging Personal Correspondence With:

Rofen, Bob. Big thanks for straightening me out as usual re Kordon/Novalek's products and various pharmacological issues. Whitney, Wayne & cohorts Denise and Fred of Mardel Labs for similarly apt-humbling with needed corrections and clarification.

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