How To: Instant Cycle an Aquarium/Fish Tank

Instant cycling a tank is not truly instant, rather a faster way of setting up a new tank. This process can take anywhere from one to two weeks. But it takes a few things that should already be available: Prime, cycled filter media and/or cycled sponge filter, Stability, and Stress Coat. Whether you cycle the filter media/sponge filter in another tank you already own or from a friend who is willing to cycle media first, the cycled media is key to this process. The more the better.

Please Note: This process is not suggested as a go to and should not be used with fish who are more sensitive to fluctuations but with hardier fish only. Either way, fish survival is not guaranteed during any type of fish-in cycle. Please use your best judgement and do your research on the breed of fish you have or are thinking of getting.

As stated above, the most important thing needed when instant cycling a tank is a used sponge filter and/or used media. Having both greatly improves this instant cycle process, although a used sponge filter alone will serve the purpose. Having Stability and Stress Coat is also important here. Stability is live bacteria that is added to the water to help stabilize the bacteria within the cycled media, while Stress Coat provides a synthetic slime coat to the fish which helps reduce stress (plus it’s an extra water conditioner too – although I would not recommend replacing your Prime with this).

1. Set up and fill the tank as normal, making sure to use only conditioned water. If water is added directly without conditioning it (treating with Prime), the good bacteria built up in the used filter media will die instantly, defeating the whole purpose of an instant cycle. I suggest using a double dose of Prime for this process and allowing it to sit for about five minutes in the tank while an air stone is running to ensure all chlorine/chloramines are gone before adding the cycled media.

2. Add the filters with the used filter media and/or the used sponge filter, making sure that both have been in a cycled tank for at least a couple months to ensure good bacteria growth within them.

3. Add Stability and Stress Coat following the dosage directions. Keep in mind how many gallons the décor is removing from the total water volume within the tank. i.e. For my 29-gallon tank, I always dose for 19 gallons, not the full 29 due to how much space my décor and substrate take up.

4. Turn on the filter(s) and allow them to run for a minimum of two hours before adding fish. This allows all the water to come into contact with the good bacteria within the cycled media at least twice, helping to spread the bacteria throughout the tank water. It also helps to ensure the Stress Coat and the Stability are properly distributed through the tank water before adding fish.

5. Optional (and again, use your best judgement): Add hardy fish.

If fish are added the same day, it is important that Stability and Stress Coat are added every day for the next three days minimum. This will help with keeping that good bacteria throughout the tank while the cycled media establishes itself well within the new tank. The Stress Coat will help the fish with stress levels.

Make sure to watch the levels in the tank too. If the ammonia does spike, make sure to do a water change. Keep in mind that you are not trying to keep the ammonia completely gone right now, as the ammonia is key to giving the good bacteria the foot hold it needs within the tank. A decent level of ammonia during this cycle is 0.5PPM. Any more than that, change only about a quarter of the water then test again no sooner than 12 hours after the water change. Watch for a nitrite spike (there may or may not be one). The main thing you are watching for is when the ammonia completely disappears on its own and the nitrates remain at less than or equal to 20PPM. At this point, the tank is cycled.

Within the week, the tank should be cycled. But maintain a close eye on it just in case. Check levels weekly for at least a month.

I will say this again: Do Not Do This With Any Sensitive Fish Breeds. Although this can be an efficient and quick process, it is still dangerous to any fish, especially sensitive breeds. This process can, has, and will kill a sensitive breed if added immediately. If you want to use this process to quickly set up a tank for a sensitive breed that is not going directly into the tank, that is possible. Follow all of the above rules, but the Stress Coat is not necessary. Make sure that the water is being closely monitored for Nitrite spikes. Do not do any water changes during this route, as a fish-less cycle with this procedure is still best.