Setting your aquarium and the Nitrogen Cycle explained, and how to avoid new tank syndrome.

Are you getting started with your first fish tank?! Then most probably haven’t heard about the “aquarium nitrogen cycle” Keep reading as I explain the nitrogen cycle in this very short and simple guide! When aquarium hobbyists like myself talk about the nitrogen cycle, we’re we usually refer to the specific part of the cycle where the fish waste turns into toxic nitrogen compounds like ammonia, nitrites, and nitrates. These nitrogen compounds can potentially kill your fish unless you make sure that you have plenty of microorganisms (also known as beneficial bacteria) and plants to consume the waste products. But before we start, we need to expand on the 3 different types of filtration you get for your aquarium.

It can be divided into 3 categories: Mechanical, Biological, and chemical filtration. In an ideal world and setup, you would need a filter that does at the bare minimum of both mechanical and biological. Since those are the two most important filter methods for your aquarium, which is why I would recommend looking at either a sump, canister, or good HOB (Hang On Back) Filter for your aquarium when it is a 4 foot and bigger, as these filters incorporate the below-mentioned methods of filtration. For anything below that size, a good sponge filter and a power head would work great. Below are the 3 different filter methods explained in more detail, and why they are so essential for your aquarium.

• Mechanical filtration: This is the removal or straining of solid particles from the water, which includes things like fish waste and other waste generated by your aquarium. Unfortunately, mechanical filtration cannot remove dissolved ammonia from the water. Mechanical filters catches and hold particles by physically trapping them within the filter. You then remove the sponge and clean it.
• Chemical filtration: This is the second type of filtration. This type of filtration removes waste from the water before they have a chance to decompose. This removes waste products from the water that can no longer be removed by your mechanical filters. Chemical filtration in a way is mechanical filtration on a molecular level. An example of chemical filtration would be Activated Carbon or Seachem Purigen for example.
• Biological filtration: This is the third type of filtration used at the Aquarium. This process will be explained in more detail below. But all you need to know is that this type of filtration does not remove wastes from the water; it merely transforms them into less toxic substances. These substances, like nitrate, are relatively harmless unless allowed to build up to high concentrations and, therefore, must be removed by doing regular and partial water changes. 

These are the 3 main steps of the Nitrogen Cycle:

• Step 1: When your fish eat, they produce waste products like poop and pee (Yes fish do pee!). And the same goes for invertebrates like snails and shrimp, then add to that any uneaten food, decaying plants, and other dead organisms in your aquarium. As these materials decay, ammonia is produced, which is extremely toxic to your fish and at high levels will burn the gills of fish and choke off their oxygen supply, causing them to die.
• Step 2: Next, other bacteria called Nitrobacter consume the nitrite and, in turn, release a less toxic chemical called nitrate. Nitrate requires anaerobic conditions to turn it into harmless nitrogen gas (They need lots of oxygen and water flow, hence the majority of the bacteria live in your filters). And then you do your weekly 20-30% water changes which flushes those toxins away and replace it with fresh water.
• Step 3: Bacteria called Nitrosomonas consumes this Ammonia and, in the process, creates another chemical byproduct called Nitrite, which is far less toxic than Ammonia but can still cause problems for your aquarium and fish if there is a big build-up of it. Although nitrite is toxic (preventing blood from carrying oxygen), fish can withstand roughly twice the amount of nitrite in their water when compared to ammonia.

The parameters needed to create this condition are not commonly present in new aquariums. Hence, you need to do a couple of things before you can add fish to your aquarium. Because new aquariums lack the colonies of bacteria that are necessary to provide biological filtration, the aquarium must be cycled. Cycling refers to the process of establishing and maturing the biological filter. So how do you exactly cycle your aquarium? Good question! First and foremost, DON’T BUY FISH UNTIL YOUR TANK IS CYCLED! This is one of the most critical stages in setting up your aquarium and the most common area of failure for beginner fish keepers. If you do not allow your aquarium to complete the nitrogen cycle before adding your fish.

It can result in New Tank Syndrome, or ammonia and nitrite poisoning, which can lead to the death of your tropical fish. When you set up a new aquarium, the bacterial colonies have to establish themselves at a level that can effectively deal with the nitrogen produced by your tropical fish. So, the first thing you have to give them is a place to live. These could be things like ceramic rings, lava rock, pumice stones, or any of the millions of biological media products you can buy at your local pet shops. As mentioned earlier in my article, you do not want fish in your aquarium while this is happening. Here’s how to get a strong nitrogen cycle going before adding your fish:

• Step 1: Set up your tank, get your substrate in, fill it with tap water, and add dechlorinator, your decorations, rock, wood, plants, etc.
• Step 2: Add your filters and remember to add some biological media, so your bacteria have a place to create their colonies in.
• Step 3: Take a pinch of fish flakes and add it to your aquarium. As it rots, the ammonia it gives off will feed the Nitrosomonas. If you want to speed up the process even quicker, you can clean another already established aquariums filter media in the new aquariums water. We call this process “seeding” because you are introducing old bacteria into a new aquarium.
• Step 4: Wait. Seriously, just make sure the water’s topped off and the equipment is operating normally, like your filters, heaters, and light you need to run your aquarium like it already has fish in it. And remember to do a 20-30% water change at the end of each week.
• Step 5: Wait some more. It can take from five days to two weeks for the cycle to complete. If the bacteria have nowhere to live (no surface area), it can take a month or more, and then it’s still possible the colonies don’t grow large enough to support tank life. Make sure you have a place for them to live.
• Step 6: At some point in the process, you’ll notice the beginnings of life in our sterile aquarium, in the form of an algae bloom. This is a sign that the cycle is nearing completion, there are enough nitrates in the tank to support algae now. This is a good thing, you might also see a slime coat on everything that is called “biofilm” which is part of the process so don’t worry about it.
• Step 7: Get your water tested. Either do it yourself or have your local pet shop test it for you. If you are testing it yourself, I would highly recommend a liquid test kit. As they are far more accurate than the test strips, there should be trace Ammonia, zero nitrites, and somewhere around 20ppm Nitrates. If that is the case, then you are ready to add your fish!

But this isn’t the end of the cycle. To keep your tank healthy, you’ll need to determine your water change schedule. The frequency and amount of the change are dependent on the bioload in your tank (The amount of fish you keep in your aquarium, I always recommend understocking your aquarium). If you have a bunch of hungry fish, then you’ll be doing anywhere between 20-30% weekly water changes. If your tank is lightly stocked, you could get away with changing our water every two weeks, or maybe even monthly. Here’s how to determine your schedule: Start by performing a 10% water change weekly. Try to be consistent (Every Sunday, for example). Twenty-four hours after your water change, test the Nitrates in your water.

It will take at least a month of weekly changes and tests to determine if your Nitrate levels are going up or down, depending on your aquarium size. If you notice, after a month, that the Nitrates aren’t staying below 20ppm, then you’re running a high bioload, and you need to increase the amount of water you are changing each week. However, if your Nitrates are zero, or hover near there, try doing only a 10% water change every two weeks and continue to monitor. Some helpful tips, never overfeed your fish as rotten uneaten food will cause an Ammonia spike, also try adding some live plants as they will absorb some of the Ammonia and Nitrates. Also, stay away from any “bacteria in a bottle” it is a waste of money and does not work.

This all might seem daunting extremely daunting at first, but you will soon get the hang of your aquarium’s nitrogen cycle. This means you will have fewer sick fish, and you will then have more time to enjoy the hobby and your new fish! If you are looking to setup a new aquarium, My Tanklife stocks various items and filters that will greatly help you with setting up a new aquarium. And which will help you avoid all the problems that I have mentioned in this article. Happy fish keeping!