Tank Cycling


The Nitrogen Cycle

The nitrogen cycle starts out with food and fish waste, this is called detritus. This detritus starts to break down and release ammonia. This ammonia starts converting to nitrite through beneficial bacteria that ‘eats’ the ammonia. The nitrites then convert to nitrates which ‘eats’ both ammonia and nitrites and makes the water safe for your fish. As more ammonia and nitrites are produced, more nitrates are produced and the cycle begins simultaneously all over again. With a properly cycled tank, your nitrates will be able to keep up on your ammonia. Keep in mind nitrates can get excited and overproduce, testing nitrates is just as important as testing your ammonia and nitrites regularly

Supplies Needed

  • An API Liquid Test Kit or other water testing kit

    • We do not recommend strips as they are typically inaccurate and test in too wide of ranges to keep up on maintenance, and can be expired. Strips can be used as a backup, but should not be your main way to test your water

  • A filter

    • Where your beneficial bacteria will grow and make a home

  • A heater

    • Beneficial bacteria like warmer temperatures (between 78-80 degrees) to grow. If doing an axolotl or goldfish IN cycle, don’t use a heater

  • An ammonia source (Fish Food, 100% Pure Ammonia, old tank water, or a fish)

    • To feed and grow your beneficial bacteria

  • A fish tank

    • To host your filter, water, and ammonia source and future fish

Where to start? 

Research your area’s water quality, this will be able to tell you what chemicals go in your water and can give a basis for your testing. You want to know how hard your water is, what the PH is, if they add chlorine/chloramine if your water contains heavy metals, lime, etc. All of these things can determine the success or detriment to your cycle and future fish.


Test your tap water! Fill a cup with your tap water, or other water sources, and let it sit for 24-48 hours. This will give you the most accurate results especially for your PH as straight out of the tap can be lower since the minerals that affect your PH haven’t settled like they would in your tank. You’ll want to test PH, Ammonia, Nitrites, Nitrates, and KH/GH.


Once you’ve researched your area’s water and tested, you should think about what kind of fish you’re going to be putting in the tank and research the kind of water that they are happiest in.


Keep in mind that if your PH is high such as between 8-8.6, most fish will be able to still adapt to your water; especially if you purchase fish from a local fish store (LFS). If your PH is higher than 8.6 you may want to consider finding another water source, such as RODI water or jugged spring water. Post about adjusting PH in progress.


Keep in mind the size of your tank, anything under 5 gallons will be much harder to maintain a proper cycle as ammonia can climb too high for the nitrates to feed on in enough time.


If your tank is 2 gallons or smaller, you should still get a filter, but perform daily to bi-daily 75-100% water changes to keep your fish happy and healthy.


API Water Testing Kit Tips

Make sure to read all directions carefully for accurate results. It's easy to get into the flow of the other tests and then accidentally mess up your Nitrate test

All Tests

Timing is key, so make sure to set a timer. Each test needs a minimum of 5 minutes to get accurate results, so start a timer once you complete the nitrate test.


Do the tests in the order of the card and all at once, don’t wait in between vials to maximize your time.


Do not leave the tests for longer than 5-10 minutes to compare to the color chart. The longer you leave them, the darker/lighter the colors will become and give you inaccurate results

PH and HPH

If you max out the normal PH test (7.6 or dark blue), test the High PH to make sure its 7.6 or below. Remember that a steady PH is important, so don’t worry too much if you’re getting fish from a LFS and your PH is under 8.6. If over, as mentioned you should look at other water sources.

Water Changes

Maintenance of an aquarium is important to maintain a healthy environment. Remember how we said it's like a hermetically sealed room? If we go too long without a water change fish waste, uneaten food, dead/dying plant matter, ammonia, nitrites, and nitrates can all build up and work against you in keeping your fish happy and healthy.


You do not need to do water changes on a cycling tank unless your ammonia (over 4ppm) or nitrates (over 40ppm) are too high. Topping off evaporated water is completely fine, just be sure to test and add more ammonia if you need to. We suggest using a glass lid to prevent rapid evaporation.


How Much?

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 Using the chart above can help you determine how much of a water change you need to do when levels start rising outside of where you want them. How much you should do weekly during normal maintenance (once cycled) will depend on the size of your tank. If it's under 5 gallons, you’ll most likely want to do 20% water changes every few days even with a filter, though we highly recommend upgrading to a 5 gallon. If over 5 gallons, 25-50% water changes once a week are recommended. You can go off your water parameters and use the chart above when you need to do a water change, but we recommend getting into the habit of weekly water changes and not allowing level climbs until it’s too late and you NEED to do a water change. Going too long without a water change also increases your chance of crashing your cycle.

What needs to be cleaned? 

You only need to gravel vacuum for normal weekly maintenance. Besides moving decorations around to get under them with the gravel vac, there is very little need to take them out and scrub them. Algae is harmless to your fish, it is okay to let it grow on your decorations. If they’re looking exceptionally dingy, you can take a toothbrush and brush off the grime in the tank water before a water change to get it off then take out the muck so it doesn’t resettle on what you just cleaned.

Filter Maintenance

If you have a kit HOB, or off the shelf HOB filter, you most likely got filter floss enclosed carbon filters already with them. These do NOT need replacing as the directions say, this is a huge gimmick in the aquarium world. If the filter has become clogged, rinse and squeeze it out in old tank water and put back in the filter. Why? Because if you rinse it in sink water, you’re washing away and killing all that lovely beneficial bacteria that you just built up in cycling. You only need to replace these kinds of filters if they are falling apart, have new ones handy so you can add them to the filter and seed it before needing to remove the falling apart one.


Tired of falling apart carbon filters? Look into bio balls and filter floss! These are great additives for your mechanical and biological filtration and they won’t fall apart as easily. With the filter floss, just as before, you can rinse in old tank water to clear out if it's clogged, or you can replace it with new filter floss.


Sponge filters can get clogged too, and reduce its ability to pull in water, so every few months you should give it a good rinse and squeeze in old tank water to give it new life.


Canister filters also can get clogged up, so follow as before and give any mechanical elements a good rinse in old tank water.

Starting your Cycle

So you have all your supplies, you’ve done some research and figured out the water you’re using, and you’re ready to cycle! But how? In the coming sections, we’ll be going over the few different ways of cycling, and the pros and cons of each.

Fishless Cycle

This type of cycling is basically ‘feeding’ an empty tank of water whether it's with 100% Pure Ammonia or fish food. Your goal ammonia ppm (parts per million) is 2-4ppm, under 2 won’t be enough, and over 4 could be too much for the bacteria to grow and take a longer amount of time.


100% Pure Ammonia is a more precise, and cleaner, way of feeding your tank. Make sure if you are buying from the cleaning aisle or hardware store that there are no surfactants, bleach, scents, dyes, or any other additives. If you’re not sure, don’t use it! If there are no ingredients on the bottle/jug, you can usually search ‘____ brand ingredients’ and get the list. Sometimes you can also find it on a store’s app.


Using something like Dr. Tim’s Ammonium Chloride will provide a cap with an installed dropper. It is a little pricey for what you get, but one bottle should last you for a normal 3-6 week cycle with a little leftover depending on how much you need to get your required ppm of ammonia This Calculator may help you with the next step:



Start out adding by the drop, we recommend 2 drops per 1 gallon to start out. After 20 minutes test your ammonia level and add more drops as needed and test again after 20 minutes. If you add too much, do a 25% water change and test again. This will take a little experimenting, as you want to stay between that 2-4ppm of ammonia. If you’d rather not count drops every time, once you know how many drops you need you can measure in a syringe or measuring cup and pour out how much you need that way!


Add Ammonia anytime it drops below 2ppm! Once you start seeing ammonia drop, you’ll start seeing nitrites and then nitrates! Add ammonia all the way up until the day before you add fish Pros - Clean - Precise - Odorless Cons - Can be hard to obtain pure ammonia.

Fish Food/Raw Shrimp

This way of ghost feeding takes a little more patience as you have to wait for the food to rot and release ammonia to cause a spike, making it a little less precise. This also means your tank water is going to get dirty and you’ll have to clean it well at the end of the cycle. Using a piece of raw shrimp (like you’d buy from the grocery store to eat yourself) is also a viable way, but again will take a while for the ammonia to spike as it rots.


Test your ammonia daily to watch for the spike, and do water changes as needed to lower the ammonia if it goes over 4ppm. Add more food as needed, unfortunately, there’s no way of knowing how much you’ll need. Pull out the shrimp/food completely when it gets to 4ppm, and add more when it starts dropping.


If you use a nylon stocking or mesh bag, you can mitigate some of the mess that comes from putting food or a rotting shrimp in.


Pros - Replicates the natural feeding you would after a cycle

Cons - Takes longer to get an ammonia spike - Messier in the long run - Might never get an ammonia spike - Smelly over time - Could culminate detritus worms, columnaris, Aeromonas in the future.

Seeding a Tank

When we talk seeding, we’re talking about adding filter media from an already cycled tank to a new tank. Usually, your LFS will sell you, or just give you some of their filter media to help you jumpstart your cycle. You just want to be very mindful that the source you’re getting media from isn’t from a diseased tank/system. You don’t want to add parasites to your tank and infect your future fish.


If you already have a tank that is cycled, here’s how to seed a new tank: For loose filter media (such as bioballs, filter sponge/floss, etc), split the media, and add more new media to both, and put the old+new into the old and new tank. The seeded media will spread to the new media and level out in your tank. Your old tank should be unaffected, but the new tank you should still wait a few days to let the new media propagate while adding an ammonia source, before adding fish.


For carbon packets, add a new carbon packet to the old filter with the old carbon pack media and let the old seed the new with normal filter operation for a week or two. When the new tank is ready, add the new carbon packet to the new filter and run it for a few days while feeding with an ammonia source to propagate the nitrates.


For a sponge filter, just add to the tank and feed an ammonia source! This is the easiest and quickest one as you can just toss it in with a new air filter and be good to go.


Pros - Jumpstarts your new tank’s cycle with already aged media - Adds more media to your old filter - The quickest way to cycle a tank

Cons - Could possibly add parasites/disease to the tank - If not fed properly, could kill the bacteria in the old media.


This type of cycle is highly unrecommended as it will be dangerous to your fish, however, we understand sometimes it must be done.

If possible, remove all fish and put in their own smaller containers and do 100% water changes daily while doing any of the previous methods in the normal tank. Adding the water from the water changes to the cycling tank can also provide an ammonia source! If this is impossible, follow the steps below.

Using a ‘feeder’ fish to cycle your tank is cruel.


Daily testing of all water parameters will be vital to your fish’s health.


When Ammonia begins to get up to 1ppm, do a 25-50% water change. You also want to water change when nitrites start appearing and creep to 1ppm.


Once you see nitrates start popping up, you want to still continue doing water changes but do at the discretion of your other levels. If your nitrites are going down, and your ammonia is staying low (1ppm or less) for a few days, you can wait to do a water change to let the nitrates grow. Still test daily, as this will let you know when you need to do a water change.

Pros - You can keep the fish in the tank while it is cycling.

Cons - Can be stressful and detrimental to your fish’s health between the more frequent water changes and the constant rise and fall of parameters - Takes a lot longer - Can be the cause of fish diseases from stress and weakened immune systems - A lot more maintenance.

What comes first? 

Of course, first, you’ll see ammonia, then you’ll see nitrites start to pop up and go up. Next, you’ll see some nitrates. There will be quite the roller coaster of ammonia going down, nitrites going up then down, and nitrates going up, down, and back up. You just have to wait it out until everything settles out on its own,

What a cycled tank looks like

You will know your tank is cycled then you have these parameters:

0ppm Ammonia

0ppm Nitrites

10-20ppm Nitrates


If your nitrates stay steady at 40ppm, that's okay, just make sure they don’t go over 40ppm.


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When to add fish? 

You will know your cycle is ready for a fish when your ammonia drops to 0ppm within 24 hours and sustains the pattern for at least a week It is highly recommended to add one fish at a time to a newly cycled tank. This will let your nitrates adjust to each new bioload and is less likely to crash your newly cycled tank.

Information brought to you by Jessica Molitor

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