Guides

In aquaristics and fish pathology, many recommendations are often reduced to short instructions such as “add a medication”, “raise the temperature”, or “give a bath”. Yet such actions are frequently performed without understanding the underlying biological processes. The “Guides” section contains materials explaining methods of diagnosis, observation, and analysis of the condition of aquatic organisms. Particular attention is given to practical tools such as microscopy, interpretation of morphological changes, analysis of clinical signs, and objective evaluation of fish condition. The goal of these materials is to demonstrate how decisions should be made on the basis of observation and evidence, rather than relying on routine treatment recipes.

Comparison of normal and pathological findings in fish organs during necropsy

Gas Bubble Disease. Part II. Consequences.

A practical approach to fish necropsy: what is normal, what may be variation, and what indicates pathology.

Patient Size Doesn’t Matter — Why Fish Don’t Die From Diagnostics

Non-lethal fish diagnostics explained: why scrapes, smears and examinations are safe — and why severely compromised fish may die after handling.

Simple Rules for Working with Aquarium Fish

✔️ If fish are dying in the aquarium for unknown reasons: Transfer all fish to another tank. Investigate what is happening. Mass mortalities can vary: ⚠️ Different species are dying simultaneously. Different genera and families have distinct lifestyles, physiology, and immune responses. If multiple species die at once, the cause is more likely water chemistry rather than a pathogen. ⚠️ One species dies quickly and massively. This is also often related to water chemistry — the most sensitive species reacts first. ...

Surgical Procedures on Aquatic Animals

Surgical Procedures on Aquatic Animals under Anesthesia: Gentle Technique and Cosmetic Suturing Precision and a gentle approach are critical in fish and aquatic animal surgery, especially for rare or valuable specimens. Standard “mattress” or rough sutures commonly used in hatcheries are not suitable—they increase the risk of complications, necrosis, and wound dehiscence. Operating Table Setup The main water box with a pump ensures a constant water flow. The working table has a cutout for positioning the fish on its back. The pump tube is inserted into the fish’s mouth, and water flows over the gills. Wet cloth covers the fish to prevent drying. An anesthetic is added to maintain the animal in a stable state throughout the procedure. The dosage of clove oil is 0.35 ml per 10 liters. Such fish are very sensitive to it. ...

Initial Diagnostics After Fish Transportation

Let’s say your name is Lena. Or Tanya. Or maybe Alex. It doesn’t matter — what matters is that you’re curious, willing to improve your work with aquatic animals, and finally have access to a microscope (congrats!). You even got some stains? Then let’s begin. ...

Microscopy of smears vs bacterial cultures

The Smear Comes First.

Imagine this. A fish arrives at the aquarium with signs of a possible bacterial infection. There’s an ulcer, some mucus, a bit of redness. The lab technician takes a sample and sets up a bacterial culture. The results? In 3–5 days. So everyone waits. But the fish is sick now. On paper, this makes sense: the culture will tell us who’s responsible and what antibiotics might work. But meanwhile, the infection progresses. Treatment may already be in progress — and the sample was taken too late. The culture comes back with nothing. People start talking about viruses. The real cause slips through unnoticed. ...