These are often repeated bits of information that are perpetuated by people using old or incorrect information. Once it becomes "common knowledge" it continues to spread through the Internet, often being changed or over-simplified in the process. These are some examples of misinformation about fish that are frequently seen online:
Mixing medications with Focus+food – this cannot work unless you calculate the dose properly. General Cure should not be dosed orally, as the two components have two different oral doses. This article discusses that:
https://www.reef2reef.com/ams/proper-dosing-of-medicated-foods.780/
Using dietary supplements as a “medication” the best diet in the world will not stop
active infections – this is called the “chicken soup” syndrome. A proper diet is of course important for long-term fish health, it's just that changing to "great diet" will not stop active disease. Dietary deficiencies cause nutritional diseases, but that does not mean that a great diet cures parasitic disease.
Adding vitamins or food additives to the aquarium’s water – this just feeds the heterotrophic bacteria, aquatic animals, if they uptake it at all, do so slower than the bacteria does.
Nitrite is toxic to marine fish – ammonia is highly toxic to marine fish at a high pH, but the salts in the water completely de-toxify nitrite ions for marine fish. Nitrite IS deadly to freshwater fish, unless some salt is added to the water.
76 day fallow period (or longer) for Cryptocaryon – published in a paper where the co-author was also the editor for the journal. The original study was from a PhD thesis that isn’t widely available. 45 to 60 days at 81 degrees F. is a more reasonable fallow period. Fallow periods for other diseases are different.
Ramp up medications slowly – too many fish die from disease if you take too long, dealers don’t do this, should you? (the only exception is salt when you are raising the salinity or the old ionic copper/citric acid solutions).
Drip acclimating shipped fish – not if there is high ammonia. Best to match the temperature, pH and salinity and move the fish directly over and then acclimate them (with no ammonia) to your tank.
Tank Transfer Method (TTM) – this method does work, but in my opinion, it works best for ich (Cryptocaryon) and not for egg laying flukes at all. It can be very rough on fish due to ammonia and excessive handling, and already stressed fish being housed in small containers. Remember that lateral viewing of new fish is a vital tool for diagnosis....top down views in buckets or totes do not give you a good enough view of how the fish is doing. Then, just when is TTM useful given the logistics of treating diseases? If you use it as part of a quarantine process, you still need a single tank to run the fish through additional quarantine for flukes. If your DT develops ich and you want to use TTM, you can't do that and just put the fish back into the DT, the ich will still be active. That means you would run TTM, but then need to move the fish to another tank during the proper fallow period for the DT.
Using RODI and no aeration for FW dips – use aerated, pH and temperature balanced water in all cases. Tap water is fine!
Using black mollies as “canaries” – really only screens for ich,
Cryptocaryon, and can introduce euryhaline trematodes into the system.
Mortality caused by medications, years after application. Copper, formalin and cyanide have all been implicated in fish loss years after exposure – this is not borne out by histopathology or veterinary necropsy. Public aquariums all have comprehensive, proactive quarantine/treatment protocols, yet they have some of the longest-lived fish. I've done three studies since 1983 that all show that latent cyanide mortality (while often severe) always manifests itself within 30 to 50 days of exposure. Long term copper exposure has been shown to cause damage to fish, but this is ionic, not chelated copper, and the toxicity appeared during or shortly after the copper exposure.
“Stray voltage” causes fish loss or health issues – This is a red herring, stray or induced voltage (typically < 50 VAC) has no measurable affect on marine fish, as they are not grounded, so there is no electrical potential. Stray voltage has been ruled out as a cause of HLLE. True electrical shorts can harm or kill fish, as well as people. All aquariums must be plugged into GFI circuits.
