Do I Need a Fish Tank Filter?
Updated: Apr 10
Can you get by without a filter if you have live plants in your tank? If you’ve kept aquariums for a while then you probably understand the importance of having a high quality filtration set up. Having this filter is essential in keeping your aquarium water at a high quality because it removes harmful things from your tank. It also helps to keep oxygen levels in your tank high if it’s set up to disturb the surface of the water. So the main points that a filter does is remove the bad stuff and add oxygen. Could live plants do the same?
Let’s have a look at what live plants do in aquariums.
They’re mainly seen as an aesthetic improvement which help boost the appearance of your tank, but they also provide some very important benefits to it as well! Live plants, as with other plants and trees, go through the process of photosynthesis. They do this either during the day, or whenever your aquarium lights are on. They take in this light and use it to help turn CO2 (or carbon dioxide) produced by your fish from the tank water into oxygen for your fish to then breathe.
Live plants also can take in certain pollutants from the tank water including things like ammonia, nitrate, and nitrite – all of these substances are harmful for your fish so it is necessary to have them removed from the tank. Aquatic plants can also help to keep algae growth at bay because they compete for the same nutrients algae needs to grow.
Java Fern is a great option for your first live plant, as its easy to keep, grows in a range of water conditions and most fish, including the ravenous goldfish won't eat it. You can buy Java Fern here.
To read about some other plant options, read our guide on Freshwater Clean up Crews.
So if they do the same thing as filters, do you need a tank filter?
To briefly recap the last section, filters take out the bad stuff from tank water and add oxygen, live plants also take out bad stuff and replace CO2 with oxygen. Given this information you might wonder what makes live plants different to other filtration systems, because they seem to perform the same functions. So, do you really need to use a filter in your planted tank? In a nutshell, mostly yes, but sometimes no. The answer will be different depending on several factors including the tank size, how many plants you have and how many inhabitants you have in your tank currently.
You can’t simply switch out your tank filter for a few plants in your freshwater aquarium and expect everything to run smoothly as filters are so much quicker at doing their jobs. If you’ve got a large tank or a large amount of fish in there, the ability of those few plants to filter out toxins and add oxygen won’t be enough to keep up with the biological load of the tank. However, if you have a large tank and many plants with only a few fish, this collection of plants may just be enough to keep up with the production of waste and carbon dioxide your fish produce.
The issue you’ll run into is that you won’t actually know if your plants are enough to clean this waste level up unless you actually try it. Remember to cycle your tank fully before you add fish - This is still true for planted tanks and you want to give your fish the best chance they have at being happy and healthy. To read up on how to cycle your tank, read our guide on How to Set Up Your First Aquarium. To start the cycle you need to have a filter installed to get to work cleaning the water and building up a biological bacteria bank to help the tank thrive.
If you’re starting the tank with a filter then, it’s not a bad idea to just take it slowly. Add plants bit by bit over time until you feel that the filter isn’t needed, then try removing it for a while and keep an eye on water quality and cleanliness. Remember that you’ll need that biological bacteria coming from somewhere else if you remove the filter, otherwise nitrogen levels might spike and cause stress and illness to your fish. You can do this by simply letting bacteria grow on the tank surfaces or install a sponge filter.
There still remains a few reasons as to why having a filtration system in your tank is still a great thing, even if you have tons of plants. The first being that your plants will be able to get everything they need to grow from the tank, but having a filter pushing the water around will really help your plants get these important nutrients more easily, which translates to better plant growth. The filter also helps keep your water nice and clean for your fish, even with all the plants. This helps your fish stay healthy.
The bottom line here is that plants look lovely, and you should definitely add them to your tank if there’s space for them. Remember filters add oxygen but they don’t necessarily remove CO2 from the tank, whereas plants do, so this will help keep those levels in check. However, filters are incredibly efficient compared to plants in filtering the tank water, obviously. Also both fish and plants will benefit from being in water that moves.
When you go out looking for a filtration system, not all are useful in planted tanks, and some can be a real pain. The ones you’re looking for should be either the hang on back filters, or the canister filters. Undergravel filters can be good for some tanks but are definitely not recommended in planted tanks as the roots can get into the filter and damage both the filter and the plant and also affect water flow, which also brings the fish’s wellbeing into it too. Just go for the first two options to stay safe.
Hang on back filters are excellent options because they tend to be more affordable and they can be used in smaller tanks. If your tank is larger, consider a cannister filter or even buying two of the hang on back filters to get your water thoroughly cleaned. Having two filters would also help you maintain good biolocical bacteria colonies when doing water changes and cleans - you can clean out one filter, leave the other and the uncleaned filter will keep the biological bacteria you’ve created over time which will slowly build up on the clean filter too, then change the older filter next time to keep it balanced.
Canister filters are also quite easy to maintain and they’re appropriate for larger tanks. There are even spray bar attachments you can use to control the water return - keep your spray bar attachment under the water and allow for the right amount of circulation through the tank. With the water circulating like this it’s a great benefit to your plants and your fish. Because they’re larger than hang on back filters, cannister filters are usually set up underneath the tank, which means you also have a little more space inside the tank too, and unlike most hang on filters, they usually have reusable filtration media.
There are other types of filtration systems available, but you need to bear in mind the fact that your tank is planted. For that reason alone, canister and HOB filters are the most often recommended products. Also, when shopping for the right filter for your planted tank, consider whether there are fish in the tank as well, and take into account the size of your tank too.
So in short, you can either use a filter or not use a filter, but it really depends on your set up. It’s certainly possible to cultivate a thriving planted tank without a filter, but it can be a little bit tricky to accomplish. You want to make sure that your live plants are able to handle the biological load in your tank before you remove the filter and you need to take steps to ensure proper biological filtration. If you do these things, however, you can certainly keep a planted tank without a filter.
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