Planning your aquarium
Setting Up a Freshwater Quarantine Tank
Plan a separate freshwater quarantine aquarium with established filtration, suitable temperature, observation space and dedicated tools to reduce cross-contamination.
Make quarantine a separate functioning system
A freshwater quarantine tank provides a separate place to observe new fish before they join an established aquarium. It needs appropriate water quality, temperature, oxygen, space and daily care. An empty spare tank becomes useful quarantine equipment only when those needs can be met.
Isolation reduces routes by which problems can reach the resident fish; it cannot guarantee that every pathogen will be detected or excluded. UF/IFAS describes quarantine as part of a broader fish-health approach alongside suitable water, nutrition and sanitation. Agree an appropriate observation and release plan with a knowledgeable aquatic professional or fish vet, especially where there is a specific disease concern.
A divider, breeder box or mesh enclosure sharing the display's water is not an independent quarantine system. Separate water circulation and dedicated tools matter. Keep the plan manageable enough that you can observe the fish, test water and carry out necessary care throughout the period they are housed separately.
Choose space and furnishings for the actual fish
Choose dimensions for the number, adult or current size, behaviour and expected stay of the fish. There is no universal small tank that suits every arrival. Consider swimming length, aggression, shoaling needs and whether several animals can be observed without crowding or hiding from view constantly.
A simple bare-bottom layout can make waste and behaviour easier to see, with suitable smooth shelter and a cover where appropriate. However, simplicity must not remove essential species needs. Fish requiring particular substrate, cover or other conditions need a tailored arrangement rather than an indiscriminately bare box.
Use a suitable stable support and a quiet position away from direct sun and local temperature changes. Separate the system from splashes and shared drainage that could contaminate the display. A tank beside the main aquarium is not automatically isolated simply because the glass containers are different.
Prepare biological filtration before the arrivals
A new sponge filter provides a surface for biological growth; it does not arrive mature merely because it is a sponge. Establish an appropriate filter in advance, using fishless cycling or a considered transfer of healthy established media, and verify processing with suitable tests before relying on it.
The sera L60 is an air-driven sponge-filter example for a suitably sized setup. Compare the physical fit, fish load and flow with the actual quarantine plan. A manufacturer's tank-volume range is not a promise that the filter can handle any group of fish within that water capacity.
The smaller L-series option
sera L60 air-driven sponge filter
The smaller named option in sera’s air-driven L range. Consider it when the larger assembly would occupy too much of the working space.
- L60 / item 08500
- Air-driven sponge
- No motor inside the aquarium
An appropriately stocked smaller setup after checking its actual footprint, uplift position and air supply.
- Check the exact L60 assembly; do not assume L150 sponges fit.
- Air pump and suitable airline need to be planned separately.
If conditioning a spare sponge in a healthy display, consider the direction of transfer. Once it has been used with quarantined or sick fish, do not put it back into the display carrying that water and material. Use a suitable separation and disinfection or disposal plan advised for the situation; disinfected media must be re-established biologically.
Do not substantially strip the main aquarium's established filter to create the quarantine filter. That can compromise the resident fish. Plan spare capacity ahead of purchase, and postpone new arrivals if a suitable independent system cannot yet be provided.
Match the air supply and protect the pump
An air-driven filter needs an appropriate pump, airline and connections. The Tetra APS100 is one mains air-supply option to compare for the installed sponge and water depth. Output at the tank depends on the complete air circuit, so a headline pump rating cannot establish the exact flow through every filter.
A separate air supply to assess
Tetra APS100 aquarium air pump
An external air pump with a flow-control accessory. The stated 100 L/h figure describes air output, not the water moved through a sponge filter.
- 100 L/h maximum air output
- 2.5 W stated input
- 4 mm internal-diameter airline connection
An air-driven installation after checking operating depth, back-pressure and the sponge maker’s requirements.
- Airline and the non-return valve are separate according to the manual.
- Keep the pump outside the water; follow the placement and below-water-level check-valve instructions.
Follow the pump's dry-placement instructions and keep electrical connections away from splashes. Use the air-pump placement guide for the circuit checks. Never put a mains air pump into the aquarium or a wet closed container.
The Tetra CV4 is a non-return valve for a compatible airline. Install it in the instructed direction and location, and check that air still reaches the filter. It helps address reverse water flow in the specified arrangement; it does not make an unsafe electrical position acceptable or guarantee indefinite protection.
Back-siphon protection in an air line
Tetra CV4 non-return air valve
A non-return valve for a compatible aquarium airline. Fit in the indicated direction so air can reach the filter while reverse water flow is resisted.
- For compatible aquarium airline
- Directional non-return valve
- Used outside the aquarium
An air-pump installation requiring a check valve under its manufacturer’s placement instructions.
- Not an airflow regulator or a valve for canister water hoses.
- Check orientation and condition; it does not make an unsafe pump position acceptable.
Adjust circulation for the fish while preserving filtration and gas exchange. Consider a prepared backup for essential aeration rather than discovering during a power cut that the only pump is unavailable. Do not assign a universal survival time to an unaerated quarantine tank.
Provide suitable temperature and prepared water
Use the intended species' requirements and actual room conditions to decide whether heating is needed. Choose a properly fitted heater where necessary and check the water with a separate thermometer. Do not raise the temperature automatically as a quarantine rule: temperature changes and treatment requirements belong to a particular fish-health plan.
Prepare replacement water with suitable chemistry and temperature, treating tap water according to the conditioner instructions. Water from an established aquarium does not substitute for mature filter media. Nor should unknown transport water be treated as a useful biological starter for the display.
An appropriate test kit belongs beside the quarantine tank. The API Freshwater Master measures core waste compounds and pH; add hardness tests if those are needed for source-water matching or diagnosis. Use the kit's actual method and reporting units rather than relying on clear appearance.
Core water checks
API Freshwater Master Test Kit
A focused liquid kit for ammonia, nitrite, nitrate and pH. Choose it if those are the measurements you need most often.
- Ammonia
- Nitrite
- Nitrate
- pH, including high-range pH
Suits routine freshwater checks and monitoring a new filter. Add a separate hardness test when GH or KH matters to your fish or water supply.
- GH and KH require another kit.
- Several separate tests take more handling than a single strip.
Keep tools, water and handling separate
Provide dedicated nets or suitable transfer containers, siphon hose, water containers and cleaning equipment. Label and store them so they are not accidentally used in the display. Keep them away from contaminated floor water and do not share wet tools casually between systems.
UF/IFAS identifies water, equipment and people's hands as possible routes of pathogen transfer. Arrange care so the resident system is attended before the quarantined group where practical, with appropriate cleaning and hand hygiene between jobs. Isolation needs a routine, not simply a spare glass box.
Keep transport water, waste water and any treatment-containing water out of the established aquarium. Choose an appropriate disposal route for the products used and follow their labels. Surface rinsing is not necessarily disinfection, while disinfection products can themselves harm fish if residues remain.
Build a daily observation and water-check record
Observe appetite, swimming, breathing, skin and fins without repeatedly chasing or handling fish. Record changes and water results so that a professional can assess the sequence if a concern appears. Fish that seem quiet after transport still need appropriate water and oxygen; do not attribute every change to settling in.
Check ammonia and nitrite frequently, particularly after arrival, a filtration change or any treatment. A cautious starting routine is daily testing while the biological response is uncertain, with additional checks if behaviour or conditions change. Respond to a detected problem promptly using the ammonia and nitrite guidance rather than waiting for obvious distress.
Use medication only for an appropriate identified need and product-supported plan. Some treatments affect biological filtration or have species and material restrictions. Do not add several preventive treatments simply because the tank is designated quarantine. Seek fish-health advice for illness and continue water monitoring during any supported treatment.
Plan release and the next use
There is no single quarantine duration that proves all fish free of every disease. Duration, observation conditions, any testing and the decision to release should reflect species, origin, history and the concern being managed. New arrivals added partway through can change the observation plan for the group.
Before transfer, confirm appropriate water conditions and agree a suitable acclimation and handling approach. Do not transfer quarantine water into the display. Afterwards, clean and, where required, disinfect or replace equipment using an appropriate protocol. Protect the distinction between equipment that looks clean and media that still provides established biological filtration.
Common questions
Can I quarantine fish in a breeder box inside the main tank?
A box sharing the display's water cannot provide independent isolation. A quarantine system needs separate water circulation and dedicated equipment as part of an appropriate fish-health plan.
Does a new sponge filter make a quarantine tank cycled?
No. It provides filter material but needs biological establishment or an appropriate healthy-media transfer. Verify processing and water quality before relying on it with new arrivals.
Is water from the display enough to mature the quarantine filter?
No. Established biological filtration is associated primarily with colonised surfaces and suitable operating conditions. Old water alone cannot be treated as proof that a new filter can process the fish load.
How long should freshwater fish stay in quarantine?
Use a plan appropriate to the fish, origin and health concern, with suitable professional advice. No universal period guarantees freedom from every pathogen or replaces observation and water-quality management.
Should every quarantined fish receive preventive medication?
Do not apply a blanket treatment routine without an appropriate need and supported plan. Treatments have species, compatibility and filtration implications; seek knowledgeable fish-health advice rather than combining products experimentally.
Can I return the quarantine sponge to my main aquarium?
Do not return used quarantine media carrying water or possible pathogens to the display. Follow an appropriate reset, disinfection or disposal plan, remembering that disinfected media needs biological re-establishment.