Almost every fishkeeper needs to reach for a bottle of medicine at some point. But what’s in them, and how do they work?
TOM ACKRILL Founder of the Freshwater Fishkeeping Facebook page, Tom has a penchant for helping new aquarists.
MASS FARMING, WILD imports, water quality issues and stress—it’s sometimes a wonder that more fish don’t suffer from pathogenic diseases. But fish do become ill, and we as aquarists do need to treat them. The question is, what do we use?
Off-the-shelf medications have been a long staple of the hobby and have saved countless lives. But with so many of them out there, a hapless aquarist can be stuck for choice. On the following pages you’ll find some of Practical Fishkeeping’s favourites, with some suggestions of what they can and can’t do—and what they use to do it.
But first, a closer look at how some of the core fish medication ingredients work…
WHAT’S IN A FISH MEDICINE?
These are some of the most common ingredients you’ll find:
• Methylene blue
A powerful dye that also has excellent biocidal effects. When exposed to light it releases a specific type of oxygen molecule that’s highly destructive to genetic material, cell membranes, and other important things that bacteria, viruses, fungi, etc., need to survive. Should only be used as a bath—dosing the tank is a last resort as it will a) stain everything and b) likely kill your biological filter cycle.
• Malachite green
Antifungal and antibacterial, it’s primarily used as an industrial dye. How exactly it works isn’t completely understood but it’s thought that it interferes with enzymatic activity leading to death of the target.
• Formaldehyde
Also gets called formalin, which is formaldehyde in aqueous solution (often with methanol). It’s an extremely effective antiparasite treatment for organisms on the outer surfaces of fish such as in the gill tissue, as well as an effective antibacterial and antiprotozoan. It works by destroying various proteins which in turn shuts down (or ‘inactivates’) the pathogenic organism in question.
Be especially careful if using this in a confined space—it’s a known carcinogen if the vapours are inhaled.
• Acriflavine
This is really at home dealing with fungi or external protozoa – think things like whitespot (Ichthyophthirius) or velvet disease (Piscinoodinium). It works by making it especially difficult for organisms to produce the prote
