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Quarantine Tank Calculator

New fish (and plants, in some cases) carry a real risk of introducing disease or parasites. This estimates a workable quarantine tank size and a sensible observation period.

Your numbers
Recommended duration

Seed your quarantine filter ahead of time

Seed a sponge filter in your main tank's filter or sump ahead of time, so your quarantine tank has established bacteria from day one instead of cycling from scratch.

How the size estimate works

A quarantine tank doesn't need to be large or decorated — it needs to be easy to observe, easy to clean, and appropriately sized for the fish in it, using the same per-fish space logic as general stocking but with a 5-gallon practical minimum so filtration and heating stay manageable.

Why quarantine duration is a range, not a fixed number

A basic 2–4 week observation period is enough to catch most common issues (ich, fin rot, obvious parasites) before they reach your main tank. Some parasites and diseases have longer life cycles, especially at cooler temperatures, which is why an extended 4–6 week period is recommended if you're actively treating a diagnosed illness rather than just observing a healthy-looking fish.

What a basic quarantine setup needs

A bare or minimal substrate (easier to spot parasites and waste, and simpler to clean), a sponge filter (gentle and easy to disinfect or replace between uses), a heater matched to the species, and simple hiding spots like a PVC pipe or plastic plant. Avoid porous decor and substrate that's hard to fully sanitize between quarantine cycles.

Source: Quarantine duration guidance follows the observation windows commonly used in public aquarium and veterinary quarantine protocols.

Frequently asked questions

Do I really need a separate quarantine tank for every new fish?

It's the single most effective thing you can do to protect an established tank from disease introduction. It takes more setup effort upfront, but is far less costly than treating or losing an established stocked tank.

Can I quarantine new plants too?

Yes — a plant-only quarantine (even just a bucket or small container for 1–2 weeks, watching for snails, algae, or pest hitchhikers) is a good practice, especially for plants from a source that also keeps fish.

What if I don't have room for a permanent quarantine tank?

A basic bare tank can be set up temporarily and stored away between uses, as long as you keep a sponge filter cycling in your main tank's sump or filter to seed bacteria quickly when needed.

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