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Fish health decision framework
Quarantine & biosecurity
Practical quarantine, isolation, equipment and decontamination workflows for home aquariums and fish rooms.
20 practical guidesOriginal AquaNexus writingReviewed 2026-08-13
Decision-first guidance
Choose the situation that matches what you are dealing with.
These pages connect back to symptom and disease profiles where a narrower differential is needed.
Quarantine & biosecurityQuarantine versus isolation: which tank does a fish need?Quarantine manages risk from apparently healthy new arrivals; isolation separates fish that are already sick or exposed. Treating the words as interchangeable can lead to poor traffic flow and accidental cross-contamination.Quarantine & biosecurityBuilding a quarantine tank that stays biologically stableA quarantine tank is only useful if it can maintain safe ammonia, nitrite, temperature and oxygen. This guide focuses on simple equipment, observable surfaces and a plan for biological filtration before fish arrive.Quarantine & biosecurityCycling and seeding a quarantine tank without cross-contaminationBorrowing wet media from an unknown or sick system can defeat quarantine. The guide compares safer ways to establish filtration while keeping the quarantine pathway epidemiologically separate from display tanks.Quarantine & biosecurityDaily quarantine observation schedule for new fishConsistent observation is more useful than occasional staring. The schedule covers breathing, posture, appetite, waste, skin, fins, gills, social behaviour and water results at the same time each day.Quarantine & biosecurityWater-quality monitoring during quarantineSmall bare tanks can change faster than established displays. This guide shows why quarantine decisions need repeated ammonia, nitrite, temperature and pH context rather than assuming any new sign is infectious.Quarantine & biosecurityFeeding and appetite records during quarantineAppetite is an early trend marker and also affects waste load. Recording what was offered, what was eaten and whether one individual hangs back can reveal deterioration before dramatic external signs appear.Quarantine & biosecurityAcclimation is not quarantine: understanding the differenceAcclimation manages the immediate transition between water conditions; quarantine manages disease risk over time. A smooth acclimation does not prove that a new fish is free of transmissible disease.Quarantine & biosecurityKeeping nets, siphons and tools separate between aquariumsWet equipment can move water, mucus, eggs, spores, parasites and microbes. Dedicated or clearly assigned tools reduce the number of invisible links between otherwise separate systems.Quarantine & biosecurityCleaning and disinfecting aquarium nets and siphons between tanksEffective decontamination requires removing organic material first, then using an appropriate process and allowing equipment to dry when practical. A quick rinse is not the same as a controlled biosecurity step.Quarantine & biosecurityClean-to-dirty workflow for multi-tank fish roomsThe order you work through tanks matters. Healthy or high-value quarantine-free systems should generally be handled before suspect, isolation or treatment systems so hands and tools do not carry risk backwards.Quarantine & biosecurityHand, glove and splash hygiene around multiple aquariumsHands, sleeves, towels and splashes can connect tanks just as nets do. This guide focuses on practical barriers and workflow rather than attempting to make a fish room sterile.Quarantine & biosecurityMoving fish between tanks without moving disease with themMoving the fish is only one part of a transfer. Water, bags, nets, containers and destination equipment all create pathways that should be considered before a fish crosses from one system to another.Quarantine & biosecurityHospital tank versus quarantine tank: when each is appropriateA hospital tank is for treatment or close management of affected fish; quarantine is a biosecurity barrier for arrivals. Keeping those purposes separate makes observation and outbreak tracing much clearer.Quarantine & biosecurityDisease biosecurity for plants moved between fish systemsPlants can carry water, detritus, eggs, snails and other biological material between tanks even when the plant itself is not diseased. This guide focuses on keeping plant transfers from bypassing fish quarantine.Quarantine & biosecurityDisease biosecurity for shrimp, snails and other invertebratesInvertebrates may share water or equipment with fish before purchase and can transfer water or hitchhiking material into a display. The guide focuses on source history and separation without assuming every invertebrate is a fish-pathogen carrier.Quarantine & biosecurityLive-food biosecurity: reducing pathogen transfer between cultures and fishLive food can be excellent nutrition but creates another biological pathway into the aquarium. Separate culture tools, clean source water and avoiding cross-feeding between suspect systems reduce that pathway.Quarantine & biosecurityUsed aquarium equipment: cleaning, drying and quarantine before reuseSecond-hand filters, hoses, décor and tanks may carry organic debris or viable disease agents. This guide separates physical cleaning, disinfection, drying and re-establishing biological filtration.Quarantine & biosecurityDisposing of transport water, aquarium water and dead fish safely in AustraliaBiosecurity continues after the fish leaves the tank. This guide aligns hobby practice with current Australian advice not to release aquarium animals, carcasses or suspect aquarium water into waterways or stormwater.Quarantine & biosecurityDecontaminating a tank after a suspected infectious outbreakThe correct process depends on the suspected agent, materials and whether the system can be emptied. This guide explains the planning sequence—remove organic material, separate porous items, choose an appropriate method and verify the tank is safe before reuse.Quarantine & biosecurityRestocking after an outbreak: how to decide when a tank is readyA calendar date alone does not prove an outbreak is over. Restocking should follow resolution of the cause, stable water, an appropriate fallow or decontamination plan when relevant, and no unexplained continuing losses.