Let's start with the basics.
One thing that you need to know about before getting a fish tank is the nitrogen cycle, or at least the basics. This is vital, or else you end up with fish living in their own toxic waste. This is the equivalent to you living in a pool of toxic ammonia, which you would not last long in.
In simple terms, cycling is when you grow beneficial bacteria that help convert ammonia from fish poop into nitrate, which is a much safer form of nitrogen. Ammonia is extremely toxic, and has terrible effects on pretty much all living beings. Nitrate, while still being toxic in large quantities, is magnitudes safer. However, there is nothing to convert Nitrate to an even safer product, which is why we must do water changes (the act of removing water and putting in fresh water) to lower the concentration of nitrate.
How to cycle a tank
In order to cycle a tank, you must introduce ammonia into the tank through one of two ways. One is the fish-in cycle. This involves buying a cheap durable fish to produce ammonia to feed the bacteria needed to keep future fish safe. However the more recent method, the fish-out cycle, is a more recent, more humane way to cycle. This involves introducing ammonia either with pure liquid ammonia or feeding fish food to the tank. The latter method does not involve actually feeding any fish, but rather it allows for the fish food to dissolve, producing ammonia. This way, while cheap, is also known to simultaneously produce algae because of all the other nutrients dissolved into the water column. Injecting pure liquid ammonia allows you to carefully measure the amount of ammonia you introduce, allowing for more precision.
In order to measure ammonia, nitrite, and nitrate in the water column, it is near essential that you buy the API water testing kit. This will allow you to see where in the cycle you are.
Why We Need to Cycle
Why do we need to cycle? Here's an “Explain like I’m Five” version. Fish poop ammonia. This ammonia is bad. Luckily we have bacteria group A to “transform” this ammonia. This bacteria converts the ammonia into nitrite. Unfortunately, nitrite is still toxic and can still harm fish. To counteract this, we have yet another bacteria group which we will call group B. Group B “transforms” this nitrite again, converting it into nitrate, which is much less toxic than ammonia. In order to cycle a tank, we need to continually feed the bacteria by introducing ammonia (which leads to nitrites which lead to nitrates). This takes time, and generally if you don’t have supplements it will take around a month to even two months.
More On Beneficial Bacteria
Where does beneficial bacteria live? Mostly in filters. Specifically, the biological filter part of the filter. This section of the filter usually has a porous surface, which means much more surface area. This means more room for bacteria to live in. In fact, beneficial bacteria grows on every piece of surface area, but it favors high oxygen and high flow, which filters provide along with their immense amount of surface area.
Jump-starting a Cycle
Cycling an aquarium from bare bottom can take up to two months, and time is money as they say. Luckily you aren’t forced to wait it out. There are two ways to speed up the cycle without tampering with water parameters. One is to “seed-start” your aquarium by putting old media from a cycled filter. Once the necessary bacteria is established, it does not take long to multiply, which means through this method you effectively cycled the tank in one day. If you do not have another tank with used media, you can always try asking an LFS (local fish store) for some. The other way is through a bottled bacteria, purchased through a store. These also seed your filter with bacteria, although it is not as instant as the previous method. Make sure you do some quick research on the specific product, as some sell bacteria that can only survive on land, which ends up stalling your cycle as that bacteria is only useful for a couple days before it dies.
Cycling a tank is necessary for a successful fish tank. Even in a non-planted tank, the fish tank is more than a fish tank; it is a complex and living ecosystem. Making sure you take care of all other parts will result in a more complete ecosystem and ultimately a happier tank.
~Keith Kim, Featured Writer