Top Two of
Marine Parasites
Sometimes,
even when the water quality in your tank is perfect, disaster can strike. The
culprit is frequently a parasitic invasion. Just what are these intruders and
what can we do about them?
There
are many types of fish parasites found in sea water. The two most common and
problematic diseases are Cryptocaryon and Oodinium. They are often called saltwater ich and
frequently confused with each other.
Although
the organisms causing these two diseases are completely different, their life
cycles are similar. A free swimming stage attaches to the host fish. Here it
feeds and then forms a cyst. Inside the cyst, the next generation of free swimming parasites
develop to be released upon maturation.
Oodinium
usually attacks the gills first. This is where the fish is most vulnerable and
the cysts are difficult to see. As the disease progresses the cysts become more
visible on the outer portions of
the fish but are
still difficult to see. Looking down the
side of the fish aids in spotting the disease, which looks
like a sprinkle of powder.
The
gills are damaged by the infestation of Oodinium,
causing respiratory problems in the fish. To maintain needed gas exchange the
gills pump faster and the fish appears to be gasping. This is usually the first
noticeable symptom of the disease. Rubbing (or scratching) across the gravel
bed and rocks in the tank is another symptom to look for as an aid in diagnosing
Oodinium.
The
life cycle of Oodinium takes place in 6 - 12 days.
This rapid reproduction allows the disease to spread rapidly and it can quickly
take out a whole tank of fish. It is the combination of being difficult to
diagnose and rapid reproduction that makes Oodinium
the more deadly of the two parasites.
Cryptocaryon
is much easier to spot than Oodinium. The infection
may begin in the gills or on the body of the fish. Distinct white spots the
size of a large grains of salt appear as the imbedded
parasites form their cysts. As in Oodinium, rubbing
or scratching is also usually apparent.
Although
Cryptocaryon reproduces at the same rate as Oodinium, it does not appear to take down fish as
quickly. This may be attributed to a
higher resistance of fish to Cryptocaryon or because
diagnosis is often faster (thus treatment begins sooner).
In
Cryptocaryon and Oodinium
infections the tank and fish must both be treated. One method of treating the
fish is to fresh water dip them. This will explode the spores on the fish.
Adjust the pH and temperature of a few gallons of de‑chlorinated fresh
water to match the corresponding values of the tank water. Bathe the heavily
infected fish in this water for 1 - 2 minutes. Watch for signs of shock and
remove the fish immediately if this occurs.
The
fish can now be moved to a treatment tank that is dosed with a copper solution.
There are many commercially prepared solutions available that vary in strength
and dosage. Use the directions for proper dosages.
Copper
levels change over time. Activated carbon removes copper and some gets absorbed
by rock, gravel and detritus. It is best to use a copper test kit to monitor
copper levels. A good trick is to check the copper concentration in the tank
shortly after the initial dosage and use this as a guide for the proper level
to maintain. This will usually be about .15 ppm
(higher for heavily chelated copper compounds like Coppersafe). Maintain effective copper levels for about 2
weeks.
A
tank can be treated without copper by using time and temperature. Move the infected fish to a treatment
tank. In the original tank increase the
temperature to 85 - 90
degrees for 2-3 weeks. The increase in temperature speeds up the
life cycle of the parasite. As the cycle runs, the spores all release their
free swimming stages which will die without a host. This is especially useful
for tanks with invertebrates.
We
often treat the fish in the same tank if no invertebrates are present (copper
is toxic to most invertebrates at very low levels). If the disease is spotted
quickly you can skip the fresh water dip and treat the tank with a copper based
medication. There are one or two treatments on the shelves now that can even be
used in tanks with invertebrates (excluding corals). Start with a mild dose and
observe the reaction of the invertebrates. If everything looks okay then slowly
bring the dosage up to the recommendation. On the other hand, if the
invertebrates show a severe reaction, do a partial
water change to reduce the amount of medication.
Formalin
is another treatment for Cryptocaryon and Oodinium that is very effective. It is very hard on the
biological filter and is generally used only in a separate treatment tank.
Treat at the rate of 1.5 drops per gallon once a day. Continue treatment for
several days after all cysts have disappeared.
There
are several methods of preventive treatment for parasitic diseases. They do not
give 100% protection against these culprits but they will highly reduce the
number and severity of the outbreaks. Each method would require an entire
discussion in itself to cover all the details, so a brief description of the
three major methods will follow.
Ultraviolet sterilization uses a unit to run the tank water past a fluorescent light
of specific frequencies. The frequencies produced kill the small, free swimming
stages of Cryptocaryon and Oodinium.
Ozone units produce O3 (ozone) that is injected into
the water as it runs through a containment area (usually a protein skimmer).
Ozone kills the free swimming stages of the parasites. The ozone must return to
its original state, oxygen, before the water returns to the tank because it
also can be toxic to everything else. Properly designed ozone set-ups must take many factors
into account and this will be the topic for another day.
The
simplest preventive method brings us back to copper products again. A form of
copper that is very stabile and will remain in the tank at effective levels for
about 30 days is available. (It can be found under the brand name Coppersafe by Mardel Labs.) This
method is limited to "fish only" tanks. A retreatment
dose is added approximately once a month or when needed as determined by
testing.
This
information will help in the diagnoses and treatment of Cryptocaryon
and Oodinium. Many diseases are spotted more quickly
and treated with greater success as the aquarist gains experience, adding to
the enjoyment of the hobby.