Listicle: When is it cost-effective to call a veterinarian to treat your fish?

In preparation for my conference presentations, I sent one of my students on an assignment.

He had to visit a local pet store, and collect information on fish medicines, namely:

  1. Regular retail prices
  2. What diseases they are used for, and
  3. Dose rates.

I then analysed the data and compared this with an average aquarium size of 300L and a pond size of 4000L. I arrived at the following conclusions:

  • Some drugs are extremely hazardous to users (e.g. trichlorfon is an endocrine disrupting chemical [see link]; formalin is carcinogenic; malachite green is so dangerous that it’s banned for use in food-fish). Do you want excess amounts of these drugs lying around where your children or pet/s may accidentally become exposed?
  • The most expensive medicines used to “self-treat” are bacterial (e.g. triple sulpha), flukes (e.g. praziquantel), and macroparasites (e.g. trichlorfon). If you have an aquarium, it might break even, provided fish respond. If you have a pond, it is actually cheaper to get a vet out.
  • Cost of “self-treatment” is based on having a correct diagnosis initially, and it is generally based on “luck” in choosing the correct drug (it might even be easier to win the lottery).
  • But, what if, your fish disease is caused by not one, but by many disease agents? In my experience, it’s quite common for multiple diseases to be present, and compounded by environmental factors. A single type of treatment would not suffice.
  • Cautionary notes on label may be inadequate. There are dangers of simultaneous, or sequential, random administration of drugs, without caution for multi-species tank (e.g. trichlorfon has cummulative effects; malachite green is harmful to fish like loaches; copper is toxic to clownfish…).
  • Label instructions do not account for water conditions. Treatments need to take water parameters into account (e.g. temperature affects lifecycle of parasites and this is vital for timing of repeat administration; general hardness affects efficacy of drugs like tetracycline is useless at rates on the label for hardwater and marine fishes because most of the drug will be chelated).
  • Label instructions may not account for disease agent. For example antibiotics should always be given as a course to avoid antibiotics resistance (some labels suggest to only treat once, when a minimum of 2-3 repeats is required to complete a course of antibiotics). In another example, time of application of repeats for parasiticides need to address egg or encysted stages.
  • Some drugs can cause more harm than good. Antibacterials like tetracycline, triple sulpha and methylene blue are hazardous to the biofilter, causing more harm.


Treating fish by trial and error is false economy. The frustration and heartache that comes with mounting fish deaths is just not worth it.

Veterinary diagnostics and treatment examines the whole system, taking the needs of the patient, and the client into consideration when choosing the type/s of medicine/s to use.

Veterinary treatment is most cost-effective for:

  • large water volumes (>500 L),
  • valuable individual fish (expensive or rare fishes like koi, discus and marines that can cost >>$50 per animal),
  • high value fish populations (e.g. marines, discus, koi), and
  • when disease is caused by more than one agent.

Having said this, for some owners, you simply cannot put a price on pet fish. The majority of my clients consider their fish, part of their family, an heirloom, their life’s work, and their place of tranquility.

For collating this information, I’d like to give a huge thanks to Ming Jun LIM, President of the WAVMA Student Chapter, at Murdoch University, DVM-candidate 2018.

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Yours sincerely,

Dr Richmond Loh

DipProjMgt, BSc, BVMS, MPh (Pathology), MANZCVS (Aquatics & Pathobiology), CertAqV, CMAVA, NATA Signatory.
Aquatic Veterinarian & Veterinary Pathologist

Mobile Aquatic Veterinary Medical & Diagnostic Services.
Ph: +61 (0)421 822 383
Skype: thefishvet

President WAVMA 2014


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