How to Create a Self-Sustaining Aquarium
Written by: Tammy (@aquarist_tl)
If you could change one thing about the aquarium hobby, what would it be? A common answer might be: the need to do water changes. While some find tank maintenance therapeutic, others may see it as a hassle. Especially those that have multiple planted fish tanks. Having to drain and fill many aquariums every week can take up more time than we would like. So what if there was a way to reduce the amount/frequency we water change to possibly never having to do it at all? That is the topic we will be discussing in this blog post!
Understanding How Aquariums Work
Before we dive into the “how”, we need to first understand some principles of aquatic life.
Why do we need to do water changes?
Probably one of the most important topics to learn in the aquarium hobby is the nitrogen cycle. To try to put it simply, fish waste and other decomposing organic matters like decaying plants or uneaten fish food will release ammonia into the water. Ammonia is toxic and will kill the livestock in the tank. Bacteria (known as “beneficial bacteria”) living on/in the filter media, substrate, and any other surface in the aquarium, will convert ammonia into nitrites and then eventually nitrates.
Nitrates are tolerable to fish and shrimp in low amounts. A large buildup of nitrates can cause the fish to get stressed, and if high enough, can kill them. The reason we do water changes is to remove some of the nitrates out of the aquarium. For example, if your aquarium reaches 40ppm of nitrates, you can do a 50% water change to get it down to 20ppm. By doing this, you’re replacing half of the “dirty” water with clean water.
How does water stay tolerable in nature?
There’s no one performing water changes on large bodies of water like oceans, lakes, and rivers, yet fish are still able to live in them. How can this be? For the most part, oceans have such a vast amount of water that the nitrate levels are probably insignificant. Meanwhile, freshwater lakes and rivers usually have plants growing in or on the edges of the land surrounding them. Nitrates are one of the nutrients that plants need to grow, so they uptake it through their roots and out of these bodies of water, thereby cleaning the water. There’s also a denitrification process that can happen in these natural sources for aquatic life that we will go more into later.
Creating an Ecosystem
Now that we know a bit about how the waters in both aquariums and in nature are kept clean enough for fish to live in, we can try to create our own self-sustainable setups. To do this, we would need to create an ecosystem. In other words, the goal of a self-sustainable aquarium is to replicate nature in our fish tanks.
Plants: Our Biggest Helpers
The first and most important part of this setup is plants. A build like this will need a lot! This is because plants are a natural filter. As previously mentioned, when plants grow, they absorb nutrients out of their environment. Two notable ones to mention are ammonia and nitrates, the chemical compounds that are a danger for fish and other livestock. The main idea is, if you have enough plants growing in the aquarium, the need to do water changes lessens because they’re doing the work for you. So ideally, the layout of this tank should be full of plants. Preferably plants that grow fast like stem plants or floating plants, since the faster they grow, the more nutrients they will absorb.
An interesting route you could take would be to incorporate traits of a paludarium and have some of the plants growing emersed. Plants that are grown out of the water typically grow at a much faster rate, which would further assist in nitrate removal. Most aquatic plants can be grown emersed.
To accomplish this layout, you could simply build the substrate in the back high enough towards the top of the tank for plants to start growing above the surface of the water. What makes this route even more appealing is that it also opens you up to the possibility of using non-aquatic plants like terrarium plants!
Even though we know a heavily planted tank is the way to go, plants are only able to help us if they are kept in the proper conditions. The main requirements that plants need to grow are: water, light, air, nutrients, and an ideal temperature. For the aquatic plants in our aquariums, water is never an issue. Instead of air, they are able to use the oxygen and carbon dioxide found in the water. Usually, aquariums in a typical household should stay in a temperature range that is ideal for your aquarium plants. There are also heaters available to keep the temperature stable. So the remaining factors of light and nutrients are the ones that need to be addressed.
Tip: While CO2 is already naturally found in water, injecting more into the aquarium will help plants grow faster, bringing us closer to a truly self-sustainable setup!
Aquarium lighting plays a big part in plant health. Your LED light should stay on for approximately 6-8 hours a day to mimic natural sunlight. A light that is too weak or too strong can actually damage some plants, or cause algae to bloom. There’s also a particular wavelength (also known as spectrum) of lighting that plants prefer. Getting an aquarium light specifically designed to grow aquatic plants will definitely help in the long run. A light that allows the users to control the brightness would be ideal. If the light ends up being too bright, you’ll have the option to dim it.
Other than the ammonia and nitrates from fish waste and other decaying organics, plants need an assortment of nutrients to thrive. In planted aquariums, this will mostly be supplemented through the substrate or fertilizers. Planted tank substrates like UNS Controsoil are packed full of the necessary nutrients to help plants grow. Make sure to add enough for the plants to dig their roots in, at least 1 1/2 - 2 inches deep. Fertilizers like UNS Plant Food All in One can be added additionally into the water column for plants that may not be rooted into substrate.
Once you have everything you need, you can set up the aquarium!
Letting the Tank Establish
After you’ve set up the tank, you should allow the aquarium to run for at least a few weeks to make sure it's completely cycled. This step requires a lot of patience. Adding in fish to early could be detrimental to both the livestock and the tank itself. The aquarium still needs to be cycled and the plants have to get established before they can start growing.
During this period, water changes should be performed quite a bit to avoid severe algae blooms. The more time has progressed, the less water changes will be required. This is the time where your aquarium is building up the proper bacteria and other microorganisms needed to become an ecosystem, so the longer you wait, the better.
When the tank is seasoned enough, it should be ready for fish and shrimp! To stay on the safe side, keep the stocking low. The goal of the self-sustainable aquarium is to keep the nitrate level low. You don’t want to have so much fish that the plants can’t keep up with the amount of nitrates. Start with a few fish and see how well the aquarium holds up by using a test kit to test water parameters. Aquariums with CO2 injection should be able to house more fish than low-tech setups. If you’re adding only shrimp, they don’t create as much waste as fish, so there may be no need to hold back on them as much.
Deep Sand Beds
Something to mention in regards to this topic are deep sand beds. As mentioned above, denitrification is another way that nitrates are removed from the water in nature. The bacteria that perform this process convert nitrates into nitrogen gas that is then released out of the water and into the atmosphere. These bacteria are anaerobic, meaning they only exist in areas with no oxygen. So, some aquarists create a home for these bacteria through deep sand beds. Sand is usually so fine that it’s impossible for oxygen exchange to occur because of the compactness of the particles. Feel free to try and replicate this method, but note that it actually takes a very long time for the bacteria to establish. Possibly years.
I hope you’ve enjoyed reading about this topic, as it was definitely interesting to write about! A world where water changes are not required seems like the dream for most in the aquarium hobby!