How to Cycle a Tank With Old Filter Media

Cycling is the process of starting up an aquarium. In a traditional fish tank, fish use waste as food, and water quality degrades over time. Because of this, water changes are necessary to maintain good water quality in a fish tank.

How to Cycle a Tank With Old Filter Media

Cycling a tank is the same process, except that instead of adding livestock that will eventually eat waste, you initially add ammonia to trick your bacteria into thinking they are in bad conditions and thus multiplying and eating harmful toxins that may be present. I will discuss how to cycle a tank with old filter media in this article. So let us get started.

What are Old Filter Media?

As time passes, the material in filters that help purify water will become clogged with organic waste and products from the breakdown of organics. The purpose of old filter media is to provide a place for bacterial colonies (the black stuff) to develop; this leads to eventual bio-filtration breakdowns.

In most cases, when dealing with biological filtration tanks, it is recommended that old filter media not be reused to avoid potentially introducing disease into new setups or reestablishing pathogens and diseases which quarantine procedures have removed.

As well as pathogen issues, the bacteria on old filter media slowly die off over time due to lack of food – they need fresh organic material every day!

Step-wise Guide on How to Cycle a Tank With Old Filter Media

Bleach Method:

This method uses a 10% bleach solution to wipe down the tank’s surface, substrate, and decorations. This should be done during water changes, so there is little risk of contact with fish or people.

Use 10% Bleach Solution to Wipe the Tank Surface

It has been suggested that this step can be skipped if you start from fresh media. But I still recommend it be done at least once if there are unappreciated hitchhikers on your used aquaria equipment.

  • Mix 1/4 cup of bleach per gallon of water (10% solution)
  • Thoroughly clean off the gravel, rocks, and other decoration with the bleach solution (it is always best to rinse these items after they have been exposed to the bleach). If new rocks were used for the substrate, rinse with larger volumes of water to try and remove all traces of bleach.
  • Wipe the bottom of the tank with a cloth soaked in the 10% bleach solution (to expose any hitchhiking life that may have been transferred from another aquarium)

Dechlorinator Method:

This method adds aquarium de-chlorinator to the tank instead of plain old tap water, thereby removing chloramines from your new cycling process water.

Remove Chloramine's New Cycling Process Water

This step should be used when starting a new cycle or if you’ve purchased an already cycled tank that was previously treated with chloramine (this step can still help prevent extra ammonia spikes and is worth doing even if you don’t suspect chloramine). The amount of time to wait before adding fish can be achieved by using the following formula:

Several days to wait before adding fish = (10 x Number of de-chlorinator dropper-fulls added) + 2 days.

  • If you are cycling a tank with an already established biofilter, substitute tap water for the dechlorinated water and add some aquarium salt during your regular water change.

Tap Water Method:

Add tap water to the tank at about a quarter of the tank’s total volume (use only if you are cycling a new tank or have purchased a new filter with no fish). Don’t add tap water if you are adding already established filter media.

This is because salt can build up in an aquarium much faster than the typical 20% evaporation rate. Therefore, when starting from scratch, it’s best to stick with just dechlorinated/salt-free water until your bio-filters are fully established.

  • With this method, there should be almost zero risks of ammonia spikes as long as your new biofilters start working right away (i.e., as long as you don’t overdose on fish).
Add Tap Water to the Tank

Ammonia Method:

This step is not really a “method” but rather a “test” that can be performed to measure the ammonia level in your tank accurately. For example, when you add new fish or equipment, there will likely be a brief spike in ammonia levels, and this test should help determine when those levels have dropped back down again.

  • Add 1/2 teaspoon (1 gram) of aquarium salt for every 2 gallons (7 liters) of water. This raises the specific gravity of the water, making its chemical properties more similar to seawater, making it unlikely that harmful bacteria will multiply at all. Having salt present also helps prevent waste from becoming too acidic, which can be fatal to the fish.
  • Add enough ammonia until your tank has a specific gravity of 1.020 (this is ten ppm). Do this by mixing ¼ teaspoon of NH4CL (ammonium chloride) into 10 gallons (37 liters) of water, and then add that solution to your tank. Using ammonium chloride instead of ordinary household ammonia means no additives in NH4CL, and it stores better between uses.

How To Cycle a Tank In 24 Hours?

Cycling a tank in 24 hours is an important task for fish tank owners to understand. The process requires careful preparation and dedication to ensure that the environment of the tank is ready for its inhabitants.

It starts with cleaning out any debris from the tank, followed by adding appropriate levels of de-chlorinator and testing the water to make sure it is safe for fish.

Then, you must add live beneficial bacteria cultures that will help reduce toxic ammonia levels so that it can serve as a habitat for your fish. Finally, you must wait 24 hours before adding any fish or animals into the tank, allowing time for the cycle to complete fully.

Frequently Asked Questions

Can I use the old filter media cycle aquarium?

It is not recommended to use old filter media cycle aquariums as they can lead to several problems. For example, the old media can cause an increase in algae and bacteria, which will then block the filters and tanks. This will require you to replace the entire system. In addition, using old media can damage the glass and plastic tanks, which need to be replaced.

What do you do with old filter media?

Old filter media can be recycled into new filters. The media is shredded, and the pieces are then washed and dried. The shredded media is then placed in a mold to create the desired shape of the new filter.

Can I use the old tank water for cycling the new tank?

Yes, you can use old tank water for cycling a new tank. However, it is important to ensure that the old tank’s water is free of contaminants and has been treated properly. You should also disinfect the new tank before using it with old water.

What do you do with old aquarium filters?

If you have an aquarium and are planning on keeping fish, you will need to replace your aquarium filters at some point. Aquarium filters are essential for removing debris and impurities from the water that your fish live in.

There are a few things that you can do with old aquarium filters:

1. You can recycle them by taking them to a local recycling center.

2. You can compost them in a pile of organic matter such as leaves, straw, or wood chips and leave them outdoors for three to four months.

3. You can throw them away in the trash.


I hope his article has been beneficial for learning how to cycle a tank with old filter media. Thank you, and have a nice day!

You can check out – How to Clean Calcite Crystals.

Jennifer Branett
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