# Aquarium quarantine duration calculator

> Enter your quarantine tank temperature in °F and pick the risk profile that matches the fish. A 78 °F tropical tank with standard risk needs about 21–28 days — the worked example below uses the same inputs so the numbers shown here always match the calculator.

Use the interactive calculator on the page: https://petguidecalc.com/aquarium/quarantine-duration/. Enter the quarantine tank temperature in °F and pick the risk profile (standard, wild-caught, or sick-tank history). The recommendation returns a day range that covers the relevant pathogen life cycle.

## How long should I quarantine new fish?

The hobby baseline is 21–28 days, which covers the full ich (white spot) life cycle. Add 7 days if the tank runs cold (below 70 °F), 14 days for wild-caught fish (higher internal parasite rate), and 14 days if the previous tank had a disease outbreak.

## Common risk / temperature combinations at a glance

| Scenario | Water °F | Risk profile | Min days | Max days |
|---|---|---|---|---|
| Captive-bred · tropical (78 °F) | 78 | standard | 21 | 28 |
| Captive-bred · cold (66 °F) | 66 | standard | 28 | 35 |
| Wild-caught · tropical (78 °F) | 78 | wild caught | 35 | 42 |
| Wild-caught · cold (66 °F) | 66 | wild caught | 42 | 49 |
| Sick-tank history · tropical (78 °F) | 78 | sick tank history | 35 | 42 |
| Sick-tank history · cold (66 °F) | 66 | sick tank history | 42 | 49 |

Base window is 21–28 days. Cold water (< 70 °F) adds 7 days; wild-caught adds 14; sick-tank history adds 14. Extensions stack.

## How the quarantine window is calculated

Base window: 21–28 days. That range covers the ich (white spot) tomont stage, which can take up to ~28 days at room temperature before releasing free-swimming theronts — anything shorter risks bringing an infected fish into the display tank.

Cold water (< 70 °F) slows pathogen metabolism. Add 7 days so the observation window still covers the slow tail of the ich, velvet, and fluke life cycles.

Wild-caught fish carry internal parasites at a much higher rate than captive-bred stock. Add 14 days to give a visible window for worms to appear in stool or for the fish to fade under observation.

Previous disease outbreak: add 14 days on top of the base window to confirm nothing re-emerges from a latent cyst stage.

Worked example: a 78 °F tank with standard risk returns 21–28 days (Standard 21–28 day quarantine at warm tropical temperatures.). Change any input and the result updates from the same shared logic.

## Quarantine FAQ

**Q: How long should I quarantine new fish?**

The mainstream hobby baseline is 21–28 days. That window covers the full ich (white spot) tomont cycle. Extend it for cold water, wild-caught fish, or a previous disease outbreak — each adds a fixed number of days so the observation window still catches late-breaking pathogens.

**Q: Why does cold water extend the quarantine?**

Cold water (< 70 °F) slows pathogen metabolism. Ich tomonts, velvet, and flukes all replicate more slowly in cold water, so a standard 3–4 week window can miss the slow tail of the life cycle. The calculator adds 7 days for cold setups.

**Q: Do wild-caught fish need a longer quarantine?**

Yes. Wild-caught fish carry internal parasites at a much higher rate than captive-bred stock. The calculator adds 14 days to give a visible window for worms to appear in stool or for the fish to fade under observation.

**Q: What if the previous tank had a disease?**

When you are cycling a fresh quarantine setup after a disease outbreak in the old tank, add another 14 days on top of the base window to confirm nothing re-emerges from a latent cyst stage. The extensions stack if more than one risk factor applies.

**Q: Can I shorten the window if the fish looks healthy?**

No — most pathogens go through a subclinical incubation period. Even a fish that looks fine on day 7 may shed ich theronts on day 21. Stick to the recommended window so the observation covers the full pathogen life cycle.

## References

The 3–4 week baseline and the risk-based extensions come from mainstream aquarium hobby sources; the calculator applies the same baseline and adds the same extensions.

- [Fish quarantine: current practices in public zoos and aquaria](https://doi.org/10.1638/2011-0034.1) — Hadfield CA, Clayton LA, J Zoo Wildl Med, 2011.
- [Fish quarantine duration](https://www.tfhmagazine.com/) — Tropical Fish Hobbyist Magazine, TFH Magazine. Long-running aquarium hobby publication confirming the 3–4 week baseline and the cold-water, wild-caught, and sick-tank extensions used by the calculator.
- [How to quarantine new fish](https://www.aquariumcoop.com/) — Aquarium Co-Op, Aquarium Co-Op. Hobby reference for the 21–28 day baseline and the ich tomont life cycle that drives the recommended observation window.
- [Quarantine and prophylactics for new fish](https://www.wetwebmedia.com/) — Wet Web Media, Wet Web Media. Hobby reference confirming the wild-caught internal-parasite extension and the rationale for stacking extensions when multiple risk factors apply.

_Educational resource, not veterinary advice. PetGuideCalc — https://petguidecalc.com_