BASIC HANDLING OF FISH IN THE VETERINARY CLINIC
How to Transport Fish to the Veterinarian?
When transporting fish, it’s important to do so in a container with water from their own aquarium. This way, the water quality and temperature won’t change significantly, making the transport less stressful for the fish.
The ideal amount of water is one liter per centimeter of fish.
If the journey lasts less than 1 hour, there’s no need for extra oxygen. Otherwise, you’ll need to introduce an air stone with a portable aerator into the water.
Since one of the main causes of fish diseases is water quality deficits, it’s recommended to bring a water sample (approximately 100-120ml) collected just before transportation.
Both the fish container and the water should be clean, made of plastic or glass, and ideally have never been in contact with toxins or soaps, or have been rinsed thoroughly.
What Parameters Should You Consider?
Currently, there are colorimetric kits for measuring some parameters, allowing for easy and quick control of water quality.
If the water sample will be analyzed in less than 1 hour, it can be kept at room temperature. If not, refrigeration is recommended.
The basic parameters to control are:
pH:
Low pH levels can damage gills, among other issues.
Temperature:
Even slight changes as small as 0.5°C can affect fish health.
Ammonia and Nitrites:
Ammonia is produced by the decomposition of waste, food, and plants. Bacteria in the system convert it into nitrites and then nitrates, which are used by algae, anaerobic bacteria, and some plants as nutrients. Ammonia and nitrites are very toxic to fish and can cause gill issues and hypoxia due to the formation of methemoglobin in the blood. Therefore, it’s important for aquariums to be well-established with nitrifying bacteria before introducing any fish.
Salinity:
Only necessary for marine or brackish water aquariums.
Oxygen:
This varies with temperature and salinity, so it should be measured at home before coming to the clinic. Excess or deficiency of oxygen can be harmful.
Other parameters like chlorine, used to destroy pathogens and often present in tap water, should also be monitored as it can harm gills and be toxic.
Additional parameters like water hardness, alkalinity, and ozone don’t need to be routinely analyzed.
What to Do with a Fish at the Clinic?
Anamnesis (Medical History):
Like with any animal presented at the clinic, it’s important to conduct a thorough anamnesis. There are a series of basic questions to ask the owner:
When did the problem appear?
Are there more affected animals?
How long have you had the aquarium, and how long have you had the fish?
Do the affected individuals show changes in behavior, such as rubbing against objects or gasping at the surface?
What is their feeding routine? How, when, and with what do they feed?
How often do you perform water changes?
What type of filtration system do you have?
Have any water treatments been applied?
Have the fish been treated previously?
Physical Examination and Diagnostic Tests:
Due to the peculiarities of fish, the clinical examination differs from other species commonly seen at the clinic.
First, observe if there are abnormalities in their behavior (sitting at the bottom of the aquarium, swimming sideways, spinning, increased respiratory rate, etc.) or physical appearance (swollen abdomen, changes in color, irregularities in fins, masses, eye opacity, external wounds, etc.).
For further diagnostic tests, anesthesia should be considered whenever procedures could cause pain, stress, or worsen the pathology.
Blood samples can be taken from the caudal vein, located in the medial area of the peduncle, and blood smears, hematocrit, and even biochemistry can be performed.
Biopsies of gills and skin scrapings can be taken to rule out the presence of parasites, fungi, and pathogenic bacteria. The external appearance of the gills can also be indicative of some diseases, so they should be thoroughly examined.
Under anesthesia, more specific diagnostic techniques like ultrasound or radiography can be conducted.
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How to Anesthetize a Fish?
Most anesthetics used in fish are products that are diluted in water.
To anesthetize a fish for non-invasive diagnostic tests, you should prepare a container with water (preferably from their own aquarium or transport water) and mix it with the appropriate dose of anesthetic. The dose is calculated based on the volume of water in which it will be diluted.
Once everything is prepared, introduce the fish into the container with the anesthetic. As it breathes, it circulates water through its gills, and the anesthetic begins to take effect. You will see the fish losing balance and starting to spin. At this point, it will be sedated enough for handling. Always monitor ventilation by observing the gill covers opening and closing with each breath. If the fish is in a very deep anesthetic plane or its respiratory rate decreases, you can reduce the anesthetic dose by adding more water to the container until it remains in an appropriate anesthetic state.
To ensure ventilation and in clinical procedures that require more time, you can apply a stream of water directly into the fish’s mouth using a pump.
Once the procedure is completed, transfer the fish back to its original container so it can filter out the anesthetic and gradually wake up. If you need to stimulate respiration, you can gently move the fish forward in the water, helping water flow through its gills and eliminate the anesthetic.
The most commonly used anesthetics in fish are: alfaxan, benzocaine, clove oil, isoflurane, phenoxyethanol, propofol, and MS-222 (tricaine methanesulfonate).