Hospital and quarantine tank: the kit that saves your fish (and your tank)
The hospital quarantine tank is your aquarium’s life insurance: a complete kit costs 40 to 80 € and keeps white spot, worms and bacterial infections from arriving with every new fish. Two uses: isolating every newcomer for 3 to 4 weeks, and treating a sick fish without medicating 200 litres and killing the shrimp in the process.
Why is quarantine essential?
A pet-shop fish comes out of a stressful pipeline: intensive breeding, transport, shared sales tanks. It can look healthy while incubating white spot, velvet or gill flukes, which break out one to three weeks later. Added straight to the display tank, it infects everything; in quarantine, it infects no one, and you treat it for next to nothing in 20 litres instead of 200.
What goes in the hospital kit?
- Bare 20 to 30 litre tank (15 to 30 €): no substrate or fixed decor, so you can siphon easily and dose treatments precisely.
- Air-driven sponge filter (10 to 20 € with the pump): gentle filtration, with no carbon that would absorb the medication.
- Small 25-50 W heater (12 to 20 €) with a reliable thermostat — see our aquarium heater guide.
- Sterilizable hiding places: a terracotta pot, PVC pipe, a plastic plant — stress slows recovery.
- Thermometer, a dedicated net (never shared with the main tank) and water tests.
How do you start a hospital tank without a 4-week cycle?
Two solutions. The best: keep a spare filter sponge running permanently in the main tank’s filter, ready to transfer into the sponge filter on the day — instant biological filtration. Otherwise: fill the hospital tank with water from the main tank, add starter bacteria and change 25 % of the water every two days while monitoring nitrites, as explained in our guide to the nitrogen cycle.
How long to isolate, and how to disinfect afterwards?
Three weeks minimum for a newcomer, four for a treated fish, feeding it well and observing it daily. After use, empty everything, clean with white vinegar or very dilute bleach, rinse thoroughly and let it dry out completely: the gear goes into storage until next time. Never pour quarantine water back into the main tank.
Frequently asked questions
Does the hospital tank need to run permanently?
No — that’s its advantage: it goes up in an hour when the need arises, provided the seeded sponge is waiting in the main filter.
Can I use a food-grade plastic tub?
Yes, a new 20-30 litre storage tub (8 to 15 €) makes an excellent budget hospital. Just make sure it has never held detergent.
Should plants and snails be quarantined too?
Ideally yes: plants can carry snail eggs, planaria and algae. A dedicated one-week bath, or a treatment dip, limits the surprise guests.
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.