Updating Marine Teleost Fish Acclimation Procedures: Part 2

Quarantine, stress and acclimation were discussed in part
one of this two part series. Here we continue covering
acclimation, recovery, the role of hyposalinity therapy,
factors influencing feeding behaviors and some handy equipment
for use during acclimation and quarantine.


The percentage of fish killed directly by poor water quality
during transport is small. The largest portions of mortalities
that occur post shipment, related to the stress of transport
and handling, are due to osmotic dysfunction, impaired immune
function and stress mediated disease (Noga, 2000. Stoskopf,
1993). Recently handled and transported fish are susceptible to
opportunistic pathogens, especially bacteria that take
advantage of stress-weakened hosts (Mazeaud et. al, 1977). Most
losses occur in the first week after transport, but the
critical period extends to several weeks.

Compromises in the mucus/scale/skin barrier make
osmoregulation difficult and cause fish to become more
susceptible to opportunistic pathogens, especially bacteria.
Products that contain polymers (PVP or polyvinylpyrrolidone)
such as Pro Tech Coat Marine™ and StressGuard™
provide a temporary barrier until tissues heal and mucus layer
recovers (Carmichael & Tomasso, 1988).


Adding vitamins and highly unsaturated fatty acids (HUFA) to
the food can help fish to recover from stress (Kraul et. al,
1993; Ako et al., 1994). Non-specific defense mechanisms of the
immune system are vitally important in protecting fish (Secombs
& Fletcher,1992). Beta glucan has proven to enhance immune
function in fish and other animals as a non-specific immune
system booster that can help prevent disease and assist in
overcoming infection. Beta glucan is an ingredient in some
foods used in aquaculture. You can administer beta glucan to
your fish by adding it to their food. For further reading about
beta glucan see:


Large, rapid changes in pH and temperature are stressful to
fish. However, fish vary in their ability to tolerate changes
in temperature and pH. This makes it difficult to suggest
recommendations or guidelines as to how much to adjust these
parameters in a 24-hour period. Temperature swings influence
the metabolic rate, blood pH balance and osmoregulation. Rapid
temperature swings can also lead to swim bladder problems.
Rapid changes in pH are stressful to fish and affect blood

A temperature change of one degree Fahrenheit per hour
(1F/hour) with a maximum of just three degrees Fahrenheit to
three degrees Celsius (equal 5.4F) a day has been suggested
(Noga, 2000). Stephen Spotte suggested that if the temperature
is to be raised that the maximum change in a 24-hour period be
limited to two degrees Celsius (3.6F) and if the temperature is
lowered one degree Celsius (1.8F) (Spotte, 1979). Limiting pH
changes to .3pH units in a 24-hour period is a good guideline
(Andrews, et. al., 2003). Others suggest that the pH should not
change more than .2 to .5pH units a day unless the level is
life threatening (Noga, 2000).

Four goals that are crucial to the recovery of fish are:

  • Reducing stress with the subsequent release of stress
  • Regaining normal homeostasis including ion, osmotic, and
    acid-base balance
  • Recovery of full immune system function
  • Return of feeding behaviors

Quickly reducing stress is critical to recovery. Choose a
quiet location for the quarantine tank with dim lighting and
plenty of hiding places. Elevated stress hormone levels in the
bloodstream inhibit immune function. Minimize the stress
factors and the level of stress hormones in the blood will
begin to decline. Help the fish regain normal acid-base balance
by slowly adjusting the pH and temperature over a few days
until these parameters match your display aquarium (provided
the water parameters in your display aquarium are at acceptable

Transport stress is diagnosed clinically by a decrease in
plasma osmolarity in freshwater fish or an increase in
osmolarity in saltwater species (Carmicheal et. al, 1984.
Robertson et. al, 1988). Severely stressed fish can lose up to
10% of their body weight in 9 to 49 hours. This weight loss is
attributed to osmotic dysfunction leading to dehydration (Sleet
& Weber, 1982).

Contrary to the commonly held belief that a salinity lower
than natural seawater is stressful to marine teleost fish (bony
reef fish), reducing the gradient (difference in salinity)
between the internal fluids of fish and the surrounding ambient
water alleviates water and ion disturbance (Wedemeyer, 1996.
Carneiro &Urbinati, 2001). Fish held in water that is close
to isotonic (the salinity of the surrounding ambient water is
close to matching the internal fluids of the fish) have
increased stress resistance (Lim et. al, 2000). These fish also
display a significantly lower mortality rate at 7 days post


I suggest placing marine teleost fish directly into a
hyposaline environment during the acclimation and quarantine
period (Lowry, 2004). A salinity of 12ppt (not Specific
Gravity) is close to isotonic for bony reef fish. I prefer
keeping the salinity at 12 to 14ppt for thirty days or more.
The salinity can then be raised a few points a day until it is
close to natural seawater, or matches your display

Although studies indicate that at least some species of
marine teleost fish grow faster in a salinity of 14ppt than at
35ppt (natural seawater) (Lambert, Dutil, and Munro, 1994), I
do not suggest maintaining hyposaline conditions indefinitely.
Do not subject marine invertebrates, sharks, rayfish, “live
rock,” or “live sand” to hyposaline conditions.

Hyposalinity assists marine teleost fish in recovery five

  • Helps control external parasites
  • Helps fish to recover osmotic balance more quickly
  • Helps fish that are injured or have lost mucus protection
    to maintain osmoregulatory balance.
  • Conserves energy that can be used to recover normal
    homeostasis and for disease resistance
  • Helps fish to recover feeding behaviors more quickly

The most obvious benefit of hyposalinity therapy to marine
fish, while acclimating to captivity, is that it is a proactive
approach to dealing with external parasites. However, there are
other significant benefits for marine teleost fish.

Osmoregulatory dysfunction is an inherent part of stress in
fish. Reducing the salinity gradient between the internal
fluids of the fish and the surrounding ambient water helps them
to recover osmotic balance more quickly.

Injuries are a common occurrence during transport and
handling. Wounds or compromises to the mucus/scale/skin barrier
make osmoregulation more difficult and costly energy-wise. In
marine fish, osmotic pressure can cause fluids to leak from
wounds into the water. Reducing the salinity of the water
decreases the osmotic pressure and loss of fluids from wounds
or compromises the mucus layer.

Marine teleost fish typically consume 25 to 50% of their
metabolic energy in the process of osmoregulation. Conserving
metabolic energy makes more available for other processes such
as regaining normal homeostasis, diseases resistance, etc.

Since osmoregulatory balance is a factor influencing feeding
behaviors, it is reasonable to assume that fish that quickly
recover osmotic balance will resume feeding sooner. Fish should
regain osmotic balance more quickly in hyposaline


Factors influencing feeding behaviors

  • Security
  • Overall health
  • Temperature
  • Photo-period
  • Osmoregulatory balance

It is important that fish begin eating within a few days
after arrival. You can help the fish feel secure in their
environment in several ways. Paint the back, bottom and sides
of the quarantine tank. Place the quarantine tank in a quiet
location away from activity and noise. Keep the lighting dim
over the aquarium and provide plenty of hiding places with PVC
pipe of various sizes.

Overall health is also an important factor influencing
feeding behaviors. You can add vitamins such as Zoe™
directly to the water in the quarantine tank. Marine fish will
absorb the vitamins from the water. Vitamins can help animals
to recover overall health and they may stimulate a feeding
response. Keep an assortment of medications handy for common

As the water temperature reaches the optimal range for a
particular species of fish, they will be more likely to eat. Do
not settle for a water temperature that the animal will merely
tolerate. Make the goal to provide optimal conditions for the
animals, including temperature.

The lighting should be dim most of the time for the first
few days. Keep in mind that some species are nocturnal while
others only eat during daylight. You may have to experiment
with the lighting, as there can be some differences between
species as to how they respond to feeding in various lighting

Osmoregulatory balance is an important factor influencing
feeding behaviors. Hyposaline conditions will help fish to
regain normal osmotic balance more quickly after transport and
handling. With the return of normal homeostasis, fish will be
more likely to resume feeding behaviors.

Fish respond to colors, movement, tastes, smells and sounds
as feeding stimuli. Live foods make good starter foods although
they may not be the most nutritionally complete. Soaking foods
in garlic seems to increase feeding responses in some fish. A
few drops of cod liver oil on the food may also help. Cod liver
oil contains a lot of vitamin A so do not use it on a continual
basis, because it is possible to overdose.

Steps to better acclimation:


  1. Prepare a mature biological filter for the
    quarantine system when possible.
    Benefits: Provides
    a stable environment without exposure to toxins such as
  2. Adjust the pH and temperature in the quarantine
    tank to match those at the retailer or the shipping water
    when possible.
    Benefits: The fish can be immediately
    removed from the transport bag and allowed to swim in
    oxygenated water. This reduces stress and helps fish to
    remove lactate acid and ammonia from their body. This also
    allows for slow acclimation to changes in pH and temperature
    over days rather than minutes or hours.
  3. Employ hyposaline conditions. Benefits:
    Proactive approach to external parasites, and counteracts
    osmotic dysfunction due to the stress of transport and
  4. Use dim lighting or red light. Benefits:
    Prevents photo shock and has a calming effect on fish.
  5. Avoid removing fish from their native environment
    (water) and the use of nets.
    Benefits: Water to
    water transfer with the use of clear plastic bags or specimen
    containers prevents stress, gill collapse, lactate acid
    build-up, and reduces injuries.
  6. Get the fish out off shipment water and into
    clean oxygenated water immediately.
    Allowing fish to swim in oxygenated water away from toxins
    reduces stress, helps reduce stress hormones in the
    bloodstream, helps fish remove toxins from their body and
    provides oxygen essential to osmoregulation and other bodily
  7. Add a polymer such as found in Pro Tech Coat
    Marine™ or StressGuard™ (polyvinylpyrrolidone) to
    the quarantine tank.
    Benefits: Protects wounds and
    aids in osmoregulation.
  8. Use Beta glucan, vitamins and Omega-3 fatty
    Benefits: Beta glucan enhances immune
    function, while vitamins and Omega-3 fatty acids help
    alleviate stress and speed recovery.
  9. Withhold feeding for 24 hours. Benefits:
    Metabolic energy is directed toward functions essential to
    immediate survival such as regaining normal homeostasis.
  10. Slow acclimation to changes in temperature and
    Benefits: Less stressful on fish than quicker
    acclimation and should improve survival.

Handy equipment for acclimation and quarantine

  • Poly Filter™ by Poly Bio Marine (Chemical
    filtration pad).
  • PVC pipe for hiding places
  • Food grade Rubbermaid™ container
  • Refractometer
  • Clear poly bags and specimen containers
  • Beta glucan
  • Highly Unsaturated Fatty Acids (Selcon™)
  • Vitamins
  • Temp Gun™
  • pH test or probe
  • Non-calcareous sand
  • Polymer such as found in StressGuard™ and Pro Tech
    Coat Marine™
  • Magnifying glass
  • Test kits for ammonia, copper, etc.
  • Medications

Poly Filter™ is a chemical filtration pad that removes
toxins such as ammonia, nitrite, copper and other impurities
from water. PVC pipe is inert and easy to find at most hardware
stores. Rubbermaid containers work well as a quarantine tank. A
refractometer is a valuable tool for accurately measuring
salinity, especially important when treating fish with
hyposalinity. Clear poly bags or specimen containers are
difficult for fish to see in water and they work well for
catching and transferring fish. Beta glucan enhances immune
function. A Temp Gun™ makes a handy tool for quickly
checking the temperature in multiple aquariums and shipment
bags without opening the bags. A pH tester such as the
pH51™ by Milwaukee Instruments can be handy as well. Use
non- calcareous sand in quarantine, when necessary, for species
such as wrasse and jawfish that sleep or dig homes in the sand.
A magnifying glass can make it easier to identify lesions or
abnormalities on fish. Having medications handy for common
infections can save valuable time.


My recommendations for updating marine teleost fish
acclimation procedures are not based upon what is easiest to
do, most cost effective, quickest or even what is most
practical. My first concern is for the health and longevity of
captive fish. I believe that these animals are entitled to
benefit from all the knowledge and skill we can provide, giving
them the best possible chance of a long and healthy existence
in our care.

Acclimation involves more than merely getting fish used to
water conditions: It includes helping animals recover from
capture, transport and handling. The process of acclimation is
not complete until the animals regain their strength, adapt to
captivity, become familiar with new foods and grow accustomed
to their tankmates and the aquarist that cares for them.

One of the greatest things about marine aquarium keeping is
that the hobby is continually evolving. Our willingness to
examine new ideas and ways of doing things is one of the
hobby’s utmost strengths. As we gain knowledge and grow in our
understanding of how to apply it, methods, procedures,
equipment and other aspects change. Our skills to maintain,
culture and sustain our hobby, along with the animals in our
care, grows with each new advance.


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  6. http://www.marineaquariumadvice.com/reducing_losses_with_transport.html
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    .” Advanced
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  8. http://www.marineaquariumadvice.com/beta_glucan_biological_defense_modulator.html
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    Better Handling
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  10. http://www.marineaquariumadvice.com/no_nets_please.html
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  Advanced Aquarist

 Terry D. Bartelme

  (16 articles)

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