Diseases and Ick: Understanding and Managing Marine Parasites

Diseases and ick: a different approach

(Opinion text and sharing of experience by Stéphane Dufour, more than 30 years of aquariophily)

Before we begin: the legal context in Canada

In Canada, it is against the law to diagnose, sell or promote any treatment for animal disease unless you are a veterinarian. This text therefore has no scientific or legal value:

• I am not a veterinarian .

• This is not medical advice , but a sharing of personal experience .

• It's up to you to take inspiration from it or not.

Over the course of my life, I have handled several thousand marine fish. Although I am not a biologist, this field experience has allowed me to observe many cases of disease and to understand — in all modesty — some crucial mechanisms for the health of our residents.

1. Why this text?

I often hear that "ick" (or Cryptocaryon irritans) is a ruthless killer and cannot be eliminated without resorting to drastic methods. In my opinion, this reputation is misleading in a mature, healthy reef tank:

• The ick may go away on its own.

• The fish's immune system , if functioning at full capacity, is the key to naturally fighting this parasite.

My goal: to offer you a different approach , based on stress reduction and the creation of a stable ecosystem, rather than rushing headlong into invasive treatments (and, let's remember, often illegal without the advice of a veterinarian).

2. Ick (Cryptocaryon irritans): what it really is

• Visual appearance : white dots, like small grains of salt on the body and fins of the fish.

• Cycle : the parasite can appear, disappear (when it detaches itself to reproduce elsewhere), then reappear.

• Natural control : In an environment where fish are confident and well fed , ick is often controlled by the host's immune defenses.

A parasite not always “fateful”

Contrary to its reputation, ick is not necessarily synonymous with mass mortality, provided that:

1. The fish is not weakened by other factors (extreme stress, deficiencies, poor water quality).

2. The tank must be large enough, with hiding places and stable parameters (pH, salinity, temperature).

3. Marine velvet (Amyloodinium ocellatum): rarer, more fatal

Many aquarists confuse ick with marine velvet, a more aggressive pathology:

• Appearance : The fish appears to be covered with a fine golden dust , veil or grayish film (rather than distinct white spots).

• Symptoms : very rapid breathing, sudden apathy, drastic loss of appetite, rapid progression (can kill in a few days).

• Severity : Velvet is rare but extremely dangerous . Without treatment or a suitable environment, it can quickly decimate a tank.

Visual tip to differentiate :

• Sharp dots "like grains of salt": more likely ick.

• A sort of golden/dusty veil, panicked breathing: suspect velvet.

4. Stress: the number 1 enemy of the immune system

The mechanism that makes the difference between a fish that survives and a fish that dies is often stress . I like to compare this to a gazelle in Africa:

• When the gazelle is chased, its immune system goes into standby mode to mobilize all its energy into fleeing (muscles, breathing, etc.).

• Once the threat has passed (a few minutes), the gazelle returns to its normal state and its immunity is reactivated.

In our aquariums, stress can last for weeks :

• A fish harassed by a fellow fish or a potential predator cannot "flee" very far.

• The insistent stares of humans, the lack of hiding places, unstable water parameters… all this prolongs a stress that should have remained temporary.

• As long as the fish is stressed , its immunity does not work at 100%. As a result, the parasite gains ground.

5. Build an “anti-stress” environment

For a harmonious reef tank, a few simple rules:

1. Provide hiding places : rocks, corals, caves (natural or artificial).

2. Don't stare too much at the newcomer: remember that in his eyes, you are a predator. Let him get used to his environment.

3. Introduce gradually : start with resistant and less aggressive species, which will reassure the following ones.

4. Maintain good parameters : temperature, salinity, pH, etc. Sudden variations create additional stress.

5. Avoid overpopulation : too many fish in a restricted volume increases competition and tensions.

6. The forties: good idea or death trap?

The topic of home quarantine is controversial. In theory, isolating a new fish allows you to:

• Spot a potential pest before it infests the main tank.

• Facilitate treatment (always under veterinary supervision, otherwise it is illegal).

In practice, many quarantines are cramped tanks , without decoration or hiding places, with poorly stabilized water. The fish undergo prolonged stress there, sometimes worse than in the main tank.

• My personal opinion : I have mixed feelings . Sometimes it is better to introduce the fish directly into a large mature tank, where it will have less anxiety and better conditions, rather than keeping it in a small, stressful space.

• If you insist on quarantine, provide adequate volume , artificial hiding places and stable water to minimize stress.

Conclusion: tame, observe, respect nature

1. Ick is often less of a threat than you might think, provided you reduce stress in fish and boost their natural immunity.

2. Velvet , on the other hand, is rarer, but much more dangerous: it should not be confused with ick and you should react as quickly as possible if you suspect it.

3. Canadian law requires that you consult a veterinarian for any drug treatment.

4. Choose a calm environment , rich in hiding places, and let your fish acclimatize at their own pace.

Ultimately, my observations after more than 30 years in this field have taught me that a confident, well-fed and little-stressed fish can overcome many parasites without heavy intervention... on condition that nature and its great balances are respected.

Stephane Dufour

Passionate aquarist for over 30 years