Josh's Frogs LogoJosh's Frogs Logo

Josh's Frogs

Flash sale! 40% off Keepers' Choice Crested Geckos. Ends September 25th @ 11:59 ET.

Fall sale
HomeBlogFishless Aquarium Cycling

Fishless Aquarium Cycling


Did you know that ALL aquariums must harbor beneficial bacteria to properly maintain the health of your fish, and that all new aquariums must go through a cycle before fish can be added? This can take anywhere from a couple of weeks to a couple of months, depending on your individual situation. However, it is imperative and we’ll explain why it’s so important, how it works, and how to do it yourself via various methods.

Fishless Method

Why choose the fishless method? Although this method takes longer, it involves growing a big amount of bacteria that can ensure the growth of stable, large colonies that will be able to handle a large bio-load. As a result, you will usually be able to add all of your fish at once at the end of the cycle.

You can use pure ammonia as a source (recommended), or by breaking down organic material in the tank (like fish flakes). We recommend finding a source of pure ammonia. This is very important! Not all ammonia is the same! Many ammonia resources you find in stores has surfactants and other detergents for an added cleaning benefit. Make sure the jug says it is 100% pure ammonia and that when you shake it, it does not create suds. It also needs to be unscented.

How Does The Nitrogen Cycle Work?

Simply put: Fish waste produces ammonia, which then gets broken down by certain bacteria and converted into nitrites. These nitrites are still harmful to the fish, just less so than ammonia. Another bacteria is required to break down the nitrites into nitrates, which are the least harmful of the three. Allowing your tank time to cycle ensures the establishment of all bacteria colonies necessary to complete each step naturally.

Get Everything Ready

Fully assemble you tank with all running hardware in operation and substrates added. For the fishless cycle, fish won’t be added until the entire cycle is completed - within 6 weeks on average. Properly cycling your tank requires patience, as you iwill need to wait for the organic material you add to your tank to decay and start producing toxic waste byproducts. Sometimes more “undesirable” and hardy fish, such as inexpensive goldfish feeders, are used to create this waste to start the tank cycle. However, the fishless cycle is considered the more ""humane"" option. This is because it doesn't expose fish to ammonia and nitrites like the method above does. Since most of your bacteria will be harbored inside your filter media, be sure to stock up on biological filtration media compatible with your particular filter for maximum results.

Add Ammonia Source

This can be done by adding your pure ammonia or sprinkling fish flakes to decay. If adding pure ammonia, we recommend 2-4 drops per 5 gallons of water using a standard-sized dropper until you have raised the ammonia level to around 5 or 6 ppm. Keep adding ammonia as necessary until this level is reached.

Test Water

After a few days, use an API Freshwater Kit to check the ammonia levels. The goal is to keep the water stabilized to around 3 ppm for the next few days. Don’t let it drop below 3 ppm and continue to test every day. As the bacteria grows, ammonia is consumed, so keeping it around 3 ppm will replenish a food source for the nitrifying  bacteria to feed on.

Test For Nitrites

As you continue to test and see your ammonia level is decreasing, you should see a spike in nitrites. This is progress and exactly what you want to see! Keep adding ammonia to reach 3 ppm to continue feeding the nitrifying bacteria and further establish the colonies.

Test for Nitrates

Keep up your daily testing and add ammonia as necessary! Usually within a few weeks or so, you may notice a sudden rise in nitrates. This means that another form of bacteria is starting to colonize - the one that consumes nitrites and converts them into nitrates. You’re just another step closer to being finished with the cycle. Keep testing until eventually the nitrites suddenly drop and the nitrates are very high.

Perform 1st Water Change

When your nitrates are very high, it’s time to do you first water change - about 50%. Even though the tank still doesn’t have fish in it, be sure when adding water back to make it as close to the same temperature as possible. Extreme temperatures can shock your bacteria, killing them and losing any progress in the cycle. You would have to start all over again!

Add more ammonia after the water change to about 3 ppm and record your parameters. In the following days, your levels should seamlessly read 0 ammonia, 0 nitrites, and some nitrates. When this happens, congrats, your tank has cycled! All bacteria are now thriving and effectively breaking down organic fish waste.

Cycle Complete - Add Fish

If you used fish flakes or other organic material besides liquid ammonia to cycle your tank, you will want to gently clean your substrate with a cleaning syphon before adding your fish. While some bacteria does live in your substrate, the majority live in the filtration media in your filter. When adding fish, you may want to start off slowly to make sure your tank doesn’t crash from a sudden change in bio-load. As we mentioned previously, using pure ammonia creates the best chance of this not happening to you. It can generally take on the full bio-load. It’s very important to keep an eye on your parameters at all times during this process. Ensure all bacteria is still doing its job and keeping your ammonia at 0, nitrites at 0, and nitrates below 20 ppm. If necessary, add any temporary conditioners to help along the process.


The following suggestions provide a few ways in which you can help speed up the whole fishless process:

  • Adding filter media and/or gravel from an already cycled tank will help introduce already formed and colonized bacteria into your aquarium. This naturally will help it establish and colonize faster in your new aquarium! You can do this from either taking some bio media or gravel from one of your own tanks or borrowing from a friend. If you don’t want to mix gravel in with yours, just put it into a nylon bag (or even use pantyhose).
  • Using live plants can help speed up the nitrogen cycle, especially if they are ones coming from an already cycled tank. Live plants pull ammonia from the water through protein synthesis. Fast-growing and/or floating aquatic plant species tend to work best, such as Vallisneria, Hygrophila, Java Moss, etc.
  • Add small quantities of certified aquarium salt (¼ oz per gallon at most) to freshwater tanks to keep toxin levels healthy and reduce nitrite toxicity during and after the cycling process. This helps pose less stress on your growing bacteria, live plants, and fish (if you choose to not follow the fishless method).

Links of Interest:

Topics in this Blog