One of the most discussed topics in the saltwater aquarium hobby, especially with beginners, is the "nitrogen cycle". The nitrogen cycle is a naturally occurring phenomenon where nitrogen is turned into several different chemical make-ups as it finds its way through an ecosystem. In the aquarium hobby, the nitrogen cycle refers to a straightforward process along those same lines. If it sounds scary or intimidating, don't worry! By the end of this article, you should have a solid foundation to understanding the nitrogen cycle in an aquarium.
This cycle starts with aquarium food. Most likely, you have or want to have fish. In order to stop your fish from kicking the bucket, you need to feed them (but not too much for reasons we'll get to later). This food will be eaten by your fish and expelled as fish waste, aka poop. The waste will be broken down by bacteria and turned into ammonia. Ammonia is highly toxic for marine life. Fortunately, the ammonia is consumed and converted into nitrite by another type of bacteria. Although less toxic, nitrite is still highly toxic for marine life. Luckily for us, this nitrite can then be converted to nitrates by a different species of bacteria. Nitrates are far less toxic and even necessary for marine life at small levels. This bacteria that turns ammonia into nitrite then into nitrate is known as nitrifying bacteria. This nitrifying bacteria is key for a stable aquarium.
That is not it for the nitrogen cycle because you still need to get rid of a large portion of the nitrate. Algae will consume some levels of ammonia, but it mostly relies on nitrate to live and grow. While this is good so that your aquarium water isn't toxic for your fish and corals, it is also bad because it means you will have a bunch of ugly algae in your tank. That is unless you remove the nitrates first.
How can you remove nitrates from your aquarium? A lot of aquarium equipment centers around removing nitrates or preventing the build up of nitrates (and phosphates). For example, a protein skimmer removes organic waste from the water before it turns into ammonia, then nitrites, and last nitrates. An algae scrubber (which is different from a refugium and macroalgae reactor) harnesses the power of microalgae to remove nitrates and phosphates from the water. Nitrates will also be removed naturally with denitrifying bacteria. This bacteria turns nitrates into nitrogen gas which then leave the aquarium and into the air.
Although denitrifying bacteria is great, you can't rely on it. Unlike nitrifying bacteria which will remove all of the ammonia and nitrite, denitrifying bacteria will not remove all of the nitrates. As you have or will see by testing your own aquarium water, there are often a lot of nitrates left. Removing nitrates and phosphates is what we call "nutrient export." In order to maintain a healthy aquarium, you need to remove the nutrients before nuisance algae does it for you. We'll talk more about nutrient export later.
"Cycling" and aquarium for the first time
Although the nitrogen cycle happens on its own in an established aquarium, it takes some time for it to start. When an aquarium is first set up, there will be little to no bacteria in the aquarium. Cycling refers to an aquarium establishing the necessary bacteria for the nitrogen cycle to work properly. Without the necessary bacteria, ammonia and nitrites will remain in the water and kill or extremely harm any fish you add to the aquarium. This bacteria can be grown in a few different ways. Live rock comes with most of the bacteria you will need for your aquarium. Sand often comes beneficial bacteria as well. So, just get some live rock and call it good, right? Well, sort of.
Often times in this hobby, choices you make early on will have consequences later. For example, getting live rock may allow your tank to cycle faster, but it also significantly increases the chance of pests taking over your aquarium. Usually, those who use live rock implement a curing process, which could be a topic for a whole other article. Live rock can certainly be used correctly and for some people it makes sense. So, live rock is one way you can introduce beneficial bacteria into your aquarium to make. However, you may not want to deal with the pests.
Although there is no definitive way to set up an aquarium, it is recommended that you do whatever you can to prevent pests from entering your aquarium. If you haven't had any experience dealing with pests, it can be very frustrating even for experienced hobbyists. The best way to set up and cycle an aquarium without potentially introducing pests is with dry rock. Dry rock usually refers to man-made rock that is completely dry. How do you get bacteria to populate the aquarium with this method?
Glad you asked! The solution to this is TurboStart 900
. This is a live bacteria product that can cycle your aquarium in as little as five days. You can purchase this Aquarium Cycle Kit
from AlgaeBarn that contains both TurboStart 900 and NitroCycle. The NitroCycle will introduce the ammonia for the bacteria to consume. The TurboStart 900 provides the bacteria. With these two products you can have your tank cycled with incredible haste.
Making the nitrogen cycle work for your aquarium
You should now have a solid basic understanding of how the nitrogen cycle works in a marine aquarium. There are things that you can do to your aquarium to make this process work more efficiently and effectively.
The majority of the things you can do to ensure the nitrogen cycle works properly are done in the early stages of the tank. Possibly the most important is adding surface area. For the beneficial bacteria (which you might be tired of hearing about by now, but it is very important!) to grow and live, it needs space to live on. This space can come from a lot of places such as sand and rocks. This is why new hobbyists are often told having plenty of rock is important. Of course, it is important, but there are other ways to increase surface area without piling your tank with rocks.
Enter MarinePure Ceramic Media.
The best way to add surface area to your aquarium is with MarinePure Ceramic Media
. This product is extremely porous, meaning that it offers more surface area in a smaller amount of space. For reference, one MarinePure sphere has the same surface area as 1,350 plastic bio-balls. This very well might be the best product for adding surface area to a marine aquarium.
In order to ensure that the nitrogen cycle is working as efficiently for you as possible, be sure to add plenty of surface area. While you can certainly add more surface area after, it is most important to do this during the beginning stages of your aquarium. This way, your aquarium can become stable from the start instead of trying to do it when the tank is already cycled.
The nitrogen cycle and how it relates to algae growth
One of the main reasons hobbyists are concerned with the nitrogen cycle is because of algae growth. Often times algae is the bane of hobbyists, especially new ones. You know that fish waste and uneaten food will eventually turn into nitrates and phosphates. Those two nutrients are also the major food sources for algae. That means that if you have a high amount of either or both, algae will likely grow in your aquarium.
Before we continue, let's take a moment to discuss how algae get into the aquarium. The most annoying alga do not come from nothing. Algae such as hair algae or bubble algae are introduced into an aquarium. If you are using live rock to start your aquarium, you will almost certainly get algae in the system.
The most common way algae is introduced to an aquarium is with coral frags. Now, this doesn't mean you shouldn't have corals in your aquarium. It would be silly to avoid corals for the sake of keeping algae out of the tank. If you really want to be safe, remove the corals from the frag plugs or scrub down the plugs as much as you can without hurting the corals. With all that being said, most hobbyists do not keep nuisance algae out of their aquarium. Most of the time, algae is fought back by removing its food source: nutrients.
To avoid algae, you need to export nutrients. In a way, this is the final stage of the nitrogen cycle. There are several ways you can do this. Some of the most popular options are protein skimmers and refugiums
. Nutrient export is a whole other topic that could be its own article. Just know that you need to figure out some method of exporting nutrients. Doing that will keep the algae at bay. It is also important to restrict the amount of nutrients that go into the aquarium. Most hobbyists, though not all, feed their aquarium too much. Feeding frozen food is especially great at causing large spikes in nutrients. In case you're wondering, live foods
such as copepods do not cause nutrient spikes.
So, that is how the nitrogen cycle works and why it matters in your aquarium. With this knowledge you will be able to better understand your tank and maintain it. Happy reefing (or fish keeping)!