Every aquarium is different. Cycling speed is affected by temperature, pH, KH, available ammonia, oxygen levels, the amount of surface area available for bacteria to colonise, and more.

A completely new aquarium with no pre-cycled filter media can take 8 weeks or longer to establish on its own. Nitro Cycle can reduce this to under a week in optimal conditions.

Test ammonia and nitrite regularly. Your aquarium is cycled when both read zero and nitrate is present.

How to make my aquarium cycle faster →

Yes, fish can be added straight away. However, a fish-in cycle is not as safe or reliable as starting the aquarium without livestock. A fishless start gives the bacteria time to establish before any fish are exposed to ammonia or nitrite, and is the method we recommend.

If you choose to do a fish-in cycle, please follow these directions.

Yes. Nitrifying bacteria need ammonia to feed on and multiply. Without it, the population won't establish. For a fishless cycle, dose an ammonium chloride solution such as AquaLabs Fishless Start to maintain a steady ammonia level while the colony builds.

Always. Chlorine and chloramine kill beneficial bacteria on contact. Treat the water with a dechlorinator such as AquaLabs Vitality first — neutralisation happens within seconds, so you can dose Nitro Cycle straight afterwards.

Nitro Cycle is robust, but the following can impact an aquarium cycle.

• Chlorine or chloramine not neutralised before dosing. This will kill the bacteria outright.
• pH below 6.5 and KH below 4 dKH. Nitrification still occurs, but much more slowly. This is common in tanks running aquasoil, as most aquasoils actively lower pH and KH. Expect a longer cycle time in aquariums with aquasoil or areas with soft, acidic water.
• Low temperatures. Lower temperatures will slow the metabolism of bacteria strains in Nitro Cycle. Increasing the temperature to 26–28 °C will help.
• KH being consumed. Nitrification uses up alkalinity, so KH falls as the cycle progresses. Test it and top it up with AquaLabs KH Plus if it drops away.
• Antibacterial or antiparasitic medications, and residual copper from previous treatments. Such treatments can kill beneficial bacteria. It is recommended to avoid these treatments during aquarium start-up.
• UV sterilisers, ozone, protein skimmers and filter socks. Newly dosed bacteria are free-floating until they settle onto surfaces, and these will remove or kill them before they can establish. Switch them off, or remove filter socks, for 48 hours after dosing.
• Zeolite or ammonia-removing resins. These strip out the ammonia the bacteria need to grow. Remove them during cycling. Activated carbon is fine and can stay in.
• Large water changes during cycling, which either remove recently dosed Nitro Cycle before it has established, or remove the ammonia the bacteria are feeding on.

Store in a cool, dark place out of direct sunlight. Do not freeze. Refrigeration is not required. However, it can extend the expiry date beyond what is printed on the box.

Yes. Nitro Cycle is suitable for freshwater, brackish and marine systems, including reef aquariums. Dose at the same rate.

Yes. Dosing after medication, filter maintenance, a heavy stocking increase or an ammonia spike helps restore the biological filter quickly.