How Long Should You Let a New Fish Aquarium Cycle For?

Most beginner aquarists want a simple answer as to how long a fish tank should be cycled before filling it with all of the desired inhabitants. However, the answer may be more complicated depending on a multitude of factors.

Freshwater or Saltwater?

Freshwater aquariums are typically more forgiving than saltwater, but either kind should be cycled for at least a month. A freshwater aquarium may allow you to add a couple of small, hardy fish to get started with a 10-gallon aquarium, and up to 5 fish with a 50-gallon aquarium.

The same holds true with a saltwater fish tank in that it should cycle with damsels for four weeks also. Always add a good beneficial bacteria to the tank during and after the cycling process for the best results:

https://www.aquaticwarehouse.com/bacteria/Microbe-Lift-Night-Out-II-Bacteria-8-oz

Once cycled, try not to add more than two fish or one pre-established pair at a time.

When cycling a reef tank at Aquatic Warehouse, we never cycle with fish. Always with a sustained high-protein liquid food like Reef Mariculture’s “Oyster Eggs” added at 3 drops per 10 gallons every 3 days. Run your protein skimmer, but don’t let it collect by either turning it down, raising the level in the tank or sump, or taking off the collection cup. This will allow the “aerobic” bacteria to multiply by being given a constant measured supply of proteins. Don’t forget to add bacteria every day for 3-4 weeks to allow you to add a large supply of corals after the cycle. (People have been known to add a piece of shrimp or fish or even liquid ammonia to start the cycle, but this actually rots, and with the spikes, this super high concentration will actually kill off smaller important strains of bacteria that you desperately need later in your reef).

Choosing Fish and When to Add More

Always start with hardy fish. While it may seem appealing to add any type of fish whenever you like, that’s likely to cause disaster within the tank. It’s best to think about what fish you want in the tank and plan ahead. A hardy fish that’s compatible with future tankmates is the best first addition. Never add a bunch of fish at once, as that will overload the system. Adding one to two fish at a time and letting the water parameters stabilize is the best way to encourage equilibrium within the mini-ecosystem.

Checking Water Parameters

The main reason it’s difficult to answer exactly how long a tank should be cycled is that the water parameters need to be regularly checked. Some freshwater tanks may cycle in as little as two-and-a-half weeks, while other tanks may still be cycling after two months.

There are test kits designed to get relatively quick readings on the water quality. These kits include desired ranges and give an insight as to what needs to be done to fix the water. Water test strips are faster and easier. They give an approximation but are nowhere as accurate as the titration drops test kits like API Test Kits:

https://www.aquaticwarehouse.com/testing-/api-freshwater-master-test-kit

We don’t recommend doing water changes during the cycling period unless the levels exceed very high ranges, which shouldn’t be a problem if you follow our recommendation above. Remember that the <2 minutes feeding rule applies here—no food anywhere in the tank after 2 minutes. It’s best to underfeed during cycling than to overfeed.

How Long Does It Take?

Regularly check the water parameters of the tank to get the right answer for your tank. The tank essentially cycles every time you add something new, so make sure you wait a sufficient amount of time between adding each fish. Checking water parameters on a regular basis isn’t something that should ever be stopped, and it will help you know everything needed to maintain a healthy fish tank for all of the inhabitants.

A mini-cycle happens for each new fish with a new tank, so keep an eye on the water parameters to ensure the tank is stable before adding more new tenants. Ammonia is very stressful to new fish.

Once your tank is up and running, you’ll need to maintain it to keep your fish happy and healthy. At Aquatic Warehouse, we carry a wide array of freshwater and saltwater aquarium supplies. Check out our website, come see us in person at our store in Kearny Mesa, or give us a call at 858-467-9297 if you have any questions.