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Is my tank cycled?

Understand your water readings and choose your next step. Free guidance for freshwater and saltwater tanks, with no account required.

1. Your setup

Include fish, shrimp, snails, corals and other invertebrates.

Optional. Age alone cannot confirm a cycle.

2. Your latest test

Enter the values you read from your test kit, in ppm (mg/L). Leave unknown results blank; blank is not zero. Use the kit’s ammonia scale, not a calculated free-ammonia value.

Your answers stay in this page and clear when you reload. Anonymous usage events help us improve the tool; they do not include your readings or answers.

Make sense of your cycle

A single photo or test cannot tell the whole story. Start with what you know; missing information is welcome.

  1. Tell us whether animals are already present.
  2. Add your readings and any cycling history.
  3. Get an explanation and a practical next step.

Understand the evidence

Is eight days enough?
There is no fixed number of days that proves a cycle. A tank’s processing history matters more than its age. Established media, temperature and the cycling method can change the timeline.
Does nitrate prove the tank is cycled?
Nitrate alone is not proof. It may already be in the source water or come from fertilizer. Plants and other export processes can also keep it low. This checker does not require nitrate to reach an arbitrary threshold.
Can you read my test tubes from a photo?
This checker uses readings you confirm from your kit. Lighting, timing and camera color can change how a tube looks. Follow the kit’s mixing and reading instructions before entering results.

Cycling references: DrTim’s Aquatics · RSPCA