🥇🐠 How to Cycle a Fish Tank

How To Cycle a Fish Tank? Aquariums are a great way to bring the beauty of nature into your home. However, in order to maintain the health and happiness of your fish, it is important that you cycle your aquarium properly before adding any fish. Cycling an aquarium can be done by following these steps: starting with a clean tank; adding water conditioner to remove chlorine or chloramine from tap water; performing regular partial water changes every 2 weeks until nitrate levels have dropped below 20ppm; and then introducing new fish.

Cycling an aquarium may seem daunting at first but with these simple steps, you will soon realize how easy it really is!

How To Cycle a Fish Tank?

1. Fish-In Cycle

Basically, this involves adding fish (the more the better) into an established tank that has beneficial bacteria growing in it. The beneficial bacteria is used by the fish to break down their waste so its less toxic and thus keeping ammonia and nitrites at bay.

By stocking up on new fish, the old ones are given a chance to make room for new ones because they will eventually die through natural or unnatural causes.

A good rule of thumb when cycling an aquarium with just new arrivals is 1 week for each inch of the longest specimen’s length, usually included in the description if you bought them from an aquarium store/pet shop.

When you’re done adding the new fish in your aquarium, you’ll need to add ammonia until the levels are 10ppm. Do this by putting a few drops of neutral sodium hydroxide (washing up liquid) into your tank and then adding some pure ammonia to it.

You can test for yourself whether its ammonia or not by rinsing an extremely small amount of it on a piece of paper towel and looking at it under a microscope. If all that’s seen is tiny spheres then its just plain water with nothing dissolved.

In this case, rinse out the container again and try again but if you see what looks like fine hairs sticking together then its probably got ammonia mixed in with it so dont use any more!

After waiting about 3 days or so, do another test to see if the ammonia levels are still at around 10ppm. If it isnt, add a few more drops of washing up liquid and then start adding small amounts of water taken from an established tank until its got a reading of 10ppm or so again.

This will slowly stabilise your aquarium and you can now add the fish that was there before but removed for cycling (if any) into the new fully cycled one.

2. Cycling with Plants

(This method uses plants to promote quicker growth of microbial populations in the substrate during nitrogen cycle.)

By planting some live plants such as cabomba, anubias and java fern etc., this will help remove nitrite from the water by converting them into less toxic substances.

Depending on the substrate used, it will usually take about 1 month for plants to grow fast enough to lower nitrite levels by themselves. This is due to the fact that nitrifying bacteria are anaerobic (respiration occurs without oxygen) and so they cannot live at the same time as roots which require oxygen to survive.

Usually within a few months later, you should notice an ammonia reading in your test kit when tested. At this point, its advisable to move any active fish into another aquarium so they dont get exposed while levels of ammonia continue increasing. Once ammonia levels reach around 6ppm or over, its time for another water change by adding some more tap water into your tank until it reaches about 50% of its initial level.

As the nitrifying bacteria grow, they eat up more nutrients in your water and so the ammonia levels will decline and after a few changes to tap water (about 4-5 times), your tank should be fully cycled.

3. Cycle Fishless

Fishless Cycle is an aquarium cycling process which does not involve fish in any way as the mediums are other forms of life such as water plants, etc. These live plants are used for their ability to consume toxic substances while removing them from your aquarium environment.

Starting off with half strength water from an established tank usually works best or even pure distilled water can also be used but you would need to use trace elements later on otherwise it could possibly kill your fish.

After 100% water changes using the purest of water it is possible to obtain (distilled water), ensure that you add a small amount of ammonia every day and check the levels after a few days to see if its reached between 3-5ppm for ammonia only. Once this level has been achieved, wait between 2-4 weeks before changing about 30% of your aquarium’s volume back into tap water from an established tank at this point. This should be done in stages within a few days apart by keeping track of what percentage your tank is at and then doing another change halfway through. This will reduce any chances of shocking your fish afterwards due to sudden changes in conditions such as temperature, pH values etc.

4. Using Pre-Established Media

Using pre-established media is a simple and effective way to cycle your fish tank quickly by using the existing biological filter from an established aquarium to seed the newly setup one to speed up the process.

This should only be done once you’ve set up your tank with live plants that are known to consume nitrite (e.g cabomba, anubias, java fern etc.) in order for them to remove enough first before using pre-established filters otherwise it could take a while longer than expected due to poisoning of your new plants and thus indirectly killing off your biological filter even if ammonia levels do not increase in the water column. This method isnt recommended unless you have a small tank to start off with first and can spare some fish once you’re done.

5. Dual Filters

Dual filters are used by setting up 2 biological filters in your fish tank, the first one (aquarium filter) is responsible for mechanical filtration while the second is an activated charcoal/carbon filter that absorbs odors and discoloring substances from the water such as uneaten food.

This method is great if you want to have more control over what’s happening inside your aquarium but it does require regular checking of parameters as well as frequent cleaning of each filter in order for them to run at optimal levels especially during cycling periods where ammonia/nitrite spikes can happen within just 1 day or so after adding some more fish to your tank.

6. Over-the-Counter Products

After having tried the above methods and still not getting satisfactory results, many hobbyists then resort to using chemical products such as Cycle which contains bacteria and is available in most pet stores easily found on display or behind the counter for aquarist use. Cycle has been used successfully by some hobbyists but its very important to read the instructions from the packet carefully and follow them step by step when using this product otherwise it could fail miserably thus wasting a lot of time and money for nothing because you’re basically starting over from scratch again.

The biggest perk with Cycle is that it works well with live plants, so if you want to keep those alive even after doing a fishless cycle, Cycle could be a good option. However as Cycle is basically a binary F1 solution, adding it directly into your tank when converting from an existing setup without cycling first could also kill off your biological filter instantly because Cycle is extremely concentrated and very dangerous to aquatic life if not handled properly [see link for more info]. So its best to start of with Cycle “Light” in order to gradually convert the water conditions over time while following all the steps required on using Cycle (link above) until you’re at about 10ppm of ammonia/nitrite in which case you should then move onto Cycle Classic or Cycle Extreme depending on what level you want to reach in terms of strength etc.


1. How long does it take for a fish tank to cycle?

It all depends on how much fish you want to keep in it and the types of plants, whether they consume ammonia or nitrite. Cycle doesn’t shorten this process unless your new fish are immune to Cycle (see section above).

2. What is the best way to cycle a fish tank?

This also will depend on what type of filtration methods you intend to use however cycling with live plants is always recommended for more stable results even if it takes longer than fish-in cycling methods.

3. How do I know my fish tank is cycled?

By using test kits regularly especially when adding new fishes into your aquarium as well as observing your biological filter (plants) closely for any signs of discoloring or clogging.

4. Will my fish die if I don’t cycle the tank?

Not really, many hobbyists out there have success stories of quick cycling their aquariums as well as converting over from an existing setup to a new one without going through the Cycle process, so its up to you whether you want to complicate things or not.

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