Aquário: Tempo de Ciclagem

The nitrogen cycle: 4 to 8 weeks of patience

When you cycle a new aquarium, what you're really doing is growing two bacterial colonies in the filter media that break down toxic fish waste into something the fish can live with. Nitrosomonas turn ammonia (NH₄⁺) into nitrite (NO₂⁻), and Nitrobacter take that nitrite the rest of the way to nitrate (NO₃⁻). The two intermediates will kill fish; nitrate is the only one they tolerate, and you pull it out with water changes or plants. Count on 4 to 8 weeks at 25 °C. There are two ways to go about it. Fishless cycling means dosing pure ammonia (3–4 ppm) until both ammonia and nitrite read 0 and you see nitrate appear, which is the safer choice. Fish-in cycling uses hardy species like zebra danios or white clouds with daily 25% water changes. A bacterial starter such as Seachem Stability, Tetra SafeStart, or Fluval Cycle seeds those colonies early and can pull the timeline down to 10–21 days. Test NH₄, NO₂, and NO₃ with a liquid kit, since strips just aren't reliable. You'll know the tank is cycled when 2 ppm of ammonia disappears within 24 hours and there's no nitrite spike behind it.

Applications

Use it when you set up a new freshwater or marine tank, when you restore a tank after antibiotic treatment has wiped out the bio-filter, or when you want to avoid the mass die-off people call "new tank syndrome". It also helps you judge bioload before adding new species and condition a quarantine tank ahead of introducing breeding stock.

FAQ

Can I skip cycling if I use a filter from an old tank? You can. Moving over mature media is the fastest route there is, basically an "instant cycle" in 24–48h, as long as the donor tank is disease-free.

Does temperature affect cycling speed? Quite a bit. The bacteria are happiest at 25–30 °C, and once you drop below 20 °C the cycle can take twice as long.

Why does nitrate keep rising? Because the cycle never removes nitrate in the first place. That's the job of plants, anaerobic filters, or partial water changes. Try to keep it below 20 ppm.

Are bacterial starters worth it? The refrigerated bottles with a recent date on them (Stability, Fritz TurboStart) really do speed things up. The cheap shelf-stable stuff usually does next to nothing.