How To Cycle a Planted Tank (As Quick As Possible)

I remember how difficult it was to stay patient when I was cycling my first planted tank. However, it’s a crucial aspect of keeping your fish safe, which is why you need to do it right. Luckily I’ve come to learn it’s not difficult.

To cycle a new planted tank, one needs to add a source of ammonia. This can be some fish food that starts rotting as well as diluted store-bought ammonia. Ammonia is the food source for beneficial bacteria that will start to grow. Plants also eat ammonia, so keep the concentration around 2ppm.

Cycling a planted tank is a bit different from cycling a “regular” aquarium. If you make mistakes during this cycling process, you risk adding fish to an unsafe environment. Therefore, it’s extra important to know what you are doing. But do not worry! I’ll make sure to explain everything that you need to know right on this page of my site, let’s dive straight in!

How to start the cycle in a planted tank

A little bit further down I will briefly explain the nitrogen cycle. I will first tell you how to get the process started, because that’s what you came for.

The first thing that you should do is add water to your tank, add a filter (and turn it on) and plant your plants. You do not have to wait with adding plants to a new tank. You can basically set up the entire tank, except for the fish. The new tank is not safe for fish yet, that’s what the cycle is for.

Now that you’ve got everything running, you need to add a source of ammonia. Ammonia is the food of the beneficial bacteria that will start to grow in your filter over the coming 6 weeks. You can add an ammonia solution to your tank or add some fish food that will produce ammonia when it starts to rot.

Start the aquarium cycle with diluted ammonia

If you choose to go down the liquid ammonia road, you’ve got some experimenting to do. You want to add just enough ammonia to your tank to reach a concentration that’s between 1 and 2 parts per million (ppm). This is equal to 1 – 2 mg per liter.

While some products on the shelves may claim to be pure ammonia, it still is mostly water. The majority of the ammonia solutions on the market are either 5% or 10% ammonia. You’ll slowly need to increase the amount of diluted ammonia in your aquarium by adding small portions of the ammonia solution.

Therefore, starting with diluted ammonia only works if you own an ammonia test kit. Don’t use test-strips for this, instead go for a liquid-based test kit such as this one available here on Amazon. It can give accurate readings.

Start with some fish food as ammonia source

I personally always take the rotting fish food road. I add a sinking algae wafer to the tank which will start to decay within days. In this case I still recommend buying an ammonia test kit. Let me explain why.

A lack of ammonia breaks the cycle

If there’s not enough ammonia in a new aquarium for the growing colony of bacteria to feed on, they will die. If your colony of bacteria dies, than your tank will not be cycled because we need those bacteria. Why would there not be enough ammonia?

The most obvious reason is because you did not add enough and the growing colony of bacteria already ate everything you add. If you use liquid ammonia you’ve got a little bit more control over the amount of diluted ammonia in your tank, compared to the estimated guess work that is rotting fish food.

This reason can happen in any tank, but there’s another planted tank specific reason: plants eat ammonia. If you’re trying to get a cycle going in a planted aquarium, you’ve got to keep in mind that all your plants that are already in the tank use the dissolved ammonia as food.

Therefore, it’s even more important to keep the amount of dissolved ammonia in check when cycling a planted tank. Make sure to buy one of these ammonia test kits, they are so worth every penny you spend on them. After the tank has cycled, you can still use it because you want to periodically measure ammonia to keep your fish safe.

What does a “cycled” planted tank mean?

Although I’ve already written a comprehensive explanation that covers everything a beginner needs to know about the nitrogen cycle, I’ll provide a small recap of the basics. I still recommend that you check out this article on my site for further information.

A brand new aquarium is not fish-safe. Why? Because fish produce ammonia through their gills and their pee/poop, and that’s toxic to fish in low concentrations. To make sure an aquarium is safe to fish, there needs to be something that removes the dissolved ammonia from the aquarium water. Nitrifying bacteria, often referred to as beneficial bacteria, is just what we need.

These beneficial bacteria are housed primarily in the filter of our tanks. To grow a colony of beneficial bacteria is called “cycling” an aquarium. But why is it called a cycle?

That’s because ammonia is only the first product. Ammonia is produced by fish and rotting organic material. The first round of bacteria can convert this ammonia to nitrite that’s already less toxic. It’s still toxic, so you want as close to no nitrite in your water. Luckily there is a second set of bacteria that can convert nitrite to nitrate. Nitrate is not toxic to fish in reasonable concentrations. To prevent nitrate from building up to toxic heights, we as fish keepers perform water changes. This removes nitrate.

In a planted tank there’s something else that removes nitrates: the plants. That’s very convenient for us because the plants help us remove nitrates and can therefore replace part of the regular water changes.

How to speed up the nitrogen cycle

Speeding up the nitrogen cycle is by far one of the most popular nitrogen cycle related questions. Growing a steady colony of beneficial bacteria usually takes about 6 weeks. Fishkeepers, including myself, are impatient and want to add fish as soon as possible. There’s only one true way to reliably speed up the cycling process: adding already cycled filter media.

Cycled media means that there’s already plenty of beneficial bacteria growing in it. You can not buy cycled media in stores (that I know off) but you can take it out of another one of your own filters. From a friend’s filter is also an option obviously.

Another way to speed up the cycle is by adding commercially available nitrifying bacteria. A great example is this product on Amazon called API Quick Start. It contains bacteria, but it’s no instant way to grow an entire colony in your filter. You can test whether your aquarium is cycled by adding some ammonia, measuring the concentrations, waiting a few days and measure again. If the concentration of ammonia has decreased, and the amount of nitrite has increased, your tank is able to break down ammonia.

I would personally recommend being patient. You do not want to add fish and slowly watch them die due to ammonia poisoning.

Bart Sprenkels

I have been keeping multiple aquariums since I was 18 years old. Just like many of you, I started with two goldfish but quickly learned they were not suitable for aquariums. Later, I switched to a tropical community tank and I also have two pet musk-turtles in a bigger aquarium. You can read more about me here.

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