Can You Have a Planted Tank Without Filter?

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If you’re getting ready to set up your first planted tank, you need the right equipment in place. One of the must-have pieces is the filtration system. But is this necessary? In truth, some aquarium setups can work without a filtration system, but that’s not always the case.

Most people think that plants are already doing the hard work of keeping the environment clean and well-oxygenated. That’s partially true because live plants produce oxygen during the day, remove ammonia and CO2, and use nitrates as a nutrient source. That being said, they cannot fully replace the filtration system. Let’s see why!

Why is Filter Necessary in a Fish Tank?

A stable and clean aquatic setup requires a filtration system; simply adding live plants won’t remove that need. Plants are great additions to any environment due to their much-appreciated benefits, such as:

  • Improve oxygenation – Plants operate based on photosynthesis, allowing them to consume CO2 and produce oxygen during the day. The process goes backward in low-light conditions, causing the plants to consume oxygen and produce CO2 instead. This means that overplanted tanks tend to experience excess CO2 during nighttime which can be detrimental to your fish population. So, you need to exercise caution in this sense.
  • Balance water conditions – Your aquatic ecosystem produces ammonia and nitrites during the breakdown of fish waste, dead organic matter, food leftovers, etc. These chemicals are then converted into nitrates by the denitrifying bacteria, which then are consumed by plants. Without plants, nitrate levels may exceed the safe parameters, at which point you’ll need to perform a water change to dilute the chemical. You need to do that regularly anyway, but that’s for another topic.
  • Hide the fish – Fish require hiding areas for when they are stressed, when breeding, or looking for some rest time. Plants are great in this sense because they provide hiding areas that allow fish to regain their composure and calm down.

But however beneficial live plants may be, they cannot take over the tasks of a high-end filtration system. Artificial filters are necessary to provide the aquatic environment with all the things that plants can’t. These include:

  • Mechanical filtration – Plants absorb nitrates, dilute ammonia, and improve oxygenation. But they cannot remove the fine or large particles floating around the tank like fish waste, dead plant matter, dirt, decaying food, etc. Only a filter can eliminate them reliably. That, or you need to clean them yourself via vacuuming the substrate regularly and performing more frequent water changes.
  • Chemical filtration – Your live plants aren’t sufficient when it comes to cleansing the water of various chemicals. Nitrates can overcome plants’ ability to remove them, especially if you overfeed your fish or keep your tank overstocked. In this case, a filtration system will take over the task of cleansing the water and keeping it within the ideal parameters. Not to mention, filters based on activated carbon also remove a variety of other chemicals that plants cannot process. These including tap water chlorine, chloramines, heavy metals, etc.
  • Biological filtration – Generally, a well-cycled tank has sufficient bacteria to ensure decent biological filtration. This notion refers to the presence of nitrifying and denitrifying bacteria whose role is to convert ammonia into nitrites, nitrates, and then nitrogen gas. The problem is that these bacterial cultures only thrive in specific setups, preferably in the substrate or on porous rocks. The filter adds an additional breeding ground, offering the filter media as the ideal housing for these bacteria.
  • Water agitation – Filters create surface agitation and water currents that allow fish to breathe better. These are necessary pieces of equipment when housing fast-water fish that could use the extra currents.

In short, I would say that the filtration system is a must-have piece for your aquatic setup. The filter comes with too many benefits to ignore and achieves things that plants cannot.

Now, contrary to everything we’ve stated so far, you can have a sustainable aquatic setup without a filtration system. We’ll see what that entails shortly.

Do Aquarium Plants Filter Water?

Aquarium plants do not filter water. Plants only perform the necessary processes to cater to their own needs. Sure, the water tends to be slightly cleaner thanks to the plants’ impact on ammonia and nitrates. They also remove CO2 and improve the overall oxygenation levels. But don’t expect plants to achieve anything in terms of actually making the water clearer.

Plants have no means of eliminating floating particles or visible dirt. You require a filter for that or, at a minimum, a tight cleaning-and-maintenance schedule. Frequent water changes may also be necessary, depending on how dirty your tank gets over several days.

What do Aquarium Plants Need?

All aquarium plants require 5 basic things to survive and thrive:

  1. Water – This goes without saying. Whether the plant is fully or partially submerged, it needs plenty of water nonetheless. You should be careful in this sense when choosing your preferred plant species. Non-aquatic plants will rot and die when forced to live in the conditions that normal aquatic plants thrive. So, always stick to aquarium-specific plants.
  2. Light – Light is probably the most important factor here. Plants are photosensitive and use light, in combination with CO2, oxygen, nitrates, and other components, to perform photosynthesis. The process allows plants to use light as an energy source to break down and absorb nutrients from their environment. CO2 and oxygen are byproducts of photosynthesis, depending on the light intensity. In well-lit conditions, plants consume CO2 and produce oxygen, while in low-light/no-light conditions, they consume oxygen and produce CO2. How intense the light should depend on your plant’s needs.
  3. Nutrients – Plants require 2 forms of nutrients, macro, and micro. The main 3 macronutrients necessary are potassium, phosphorus, and nitrogen, while micronutrients comprise of numerous trace elements. These include iron, magnesium, calcium, manganese, etc. Plants usually get their macronutrients from their surrounding environment. These are generally the result of normal organic matter decay. Micronutrients need to be replenished regularly, which demands the need of frequent water changes. Most plants require additional fertilization to meet their nutritional needs.
  4. CO2 – This gas is the natural product of fish and bacterial breathing, as well as surface gaseous exchange. Plants rely on CO2 to perform their normal photosynthesis and may require CO2 injections if the naturally available CO2 is insufficient.
  5. Sufficient space – Overcrowd your plants, and they will begin to die. This is due to CO2 and nutrient competition since all plants use the same elements. So, they require sufficient space to prevent starvation and decrease the impact of nutrient scarcity.

The problem is that simply knowing what your plants need doesn’t do much for you. That’s because you also need to know how much they need of any given component. Here’s what I mean by that:

  • Light intensity and duration – How much light should your plants get, and how intense should it be? Most live plants require 8-10 hours of light, followed by low light or no light for the remaining 12-14 hours. Things get slightly more confusing when it comes to intensity. That’s because too much light promotes algae bloom which can suffocate your plants and cut their access to light. How much light your aquarium plants need depends on the species. Some thrive in low-light conditions, while others demand more power. Always inform yourself on the plant you’re getting to make sure you understand its needs.
  • How much CO2 – Plants may not require CO2 injections in aquariums overpopulated with fish. The CO2 levels are generally sufficient in that scenario, provided your tank is not overplanted.
  • The right amount of nutrients – The goal is to prevent and identify early signs of nutrient deficiency. Plants may experience nutrient deprivation, causing hindered growth, poor coloring, and overall poor health. Learning which nutrients they need and in what quantities is key to keeping your plants healthy and thriving over the years. Especially since some plants grow faster and demand more nutrients than others.

Best Plants for No-Filter Aquarium

The best plants for no-filter tanks are slow-growing, low-maintenance species. Plants like anubias, cryptocoryne, or java fern fit right in. These are easy to maintain, don’t require too much light, and thrive even in conditions that rank as sub-ideal for most other species.

Naturally, choosing the right plant species is only half the work. You also need to consider other parameters along the way, such as how many fish you have, the available nutrients, the light intensity, the available CO2 and oxygen in the water, etc.

How to Set Up a Planted Tank Without Filter?

While it is possible to set up a thriving aquatic system without any artificial filtration, keep in mind that that’s no easy task. Plants are quite effective at diluting ammonia, nitrates, and CO2 and improving oxygen levels in the environment. The problem is that it is more difficult to maintain the water’s chemical balance in a closed system like an aquarium.

To successfully set up the ideal planted tank without a filter, you must consider the number of fish, the number of plants, the plant types, and the overall layout. Aquariums overcrowded with fish will present a higher bioload that no amounts of plants could process.

The concept of setting up a planted tank without a filter is easy in theory – you test it out. Create your preferred aquatic layout, cycle the system, add your favorite plants, and throw in some fish for waste production. The exact balance between the number of fish and plants depends on the fish’s size, their waste production capabilities, and the plants’ size, metabolic rate, and nutritional needs.

There are a lot of variables to handle, as you can see. This means that there’s no golden bullet to go for. You simply have to test to see what works and what doesn’t and adjust things along the way. Just know that it can be done.

Tips to Maintain a Planted Tank Without Filter

Now that you know that you can create a sustainable aquatic environment without a filtration system let’s see how you can do that. I have several recommendations in this sense:

  • More plants – Since you don’t have a filtration system in place, the responsibility of keeping the environment clean and stable now falls onto your plants. The problem is that the system’s bioload can quickly overwhelm your plants’ abilities to displace it. You can fix such problem by adding in more plants for improved cleansing capabilities. How many plants to add depends on their size, profile (fast or slow growers), available space, etc. Just know that more is better in this sense, up to a point, of course.
  • Less fish – You can’t overpopulate your tank with fish if you don’t have a filtration system. The animals will produce more waste than your plants can filter, causing ammonia and nitrate spikes. These will kill both fish and plants over time. So, you should have more plants than fish to ensure the system’s stability.
  • Mind the CO2/Oxygen balance – Plants use photosynthesis to synthesize CO2 and oxygen based on the level of environmental light. Overplanted tanks seriously threaten your fish population because plants consume oxygen and produce CO2 during nighttime. This could cause your fish to suffocate, since they also produce CO2 around the clock. I suggest skipping fish altogether if you’re going for an overplanted aquarium. Or, at the very least, monitor CO2 and oxygen levels and improve the tank’s aeration to prevent excess CO2 accumulation during nighttime.
  • Mind light intensity – Too much light is detrimental to your plants. That’s because the excess light promotes algae overgrowth, and these will spread everywhere, including the surface of your plants. The algae will restrict the plants’ access to light, causing them to starve. Not to mention, some aquarium plants are naturally more sensitive to light, so too much could cause the plants to die.
  • Choose the right fish – Yes, choosing the right fish for your unfiltered tank is key here. Not all fish are equally as resilient, and you need some that will easily adapt to a non-filtered setup. In this sense, fish like common pleco, paradise fish, fancy guppies, white cloud mountain minnows, and neon tetras are good options.
  • Ensure optimal maintenance – The maintenance process is key in preserving the system’s stability long-term. You need to remove excess waste, change the water regularly, and clean algae deposits. It’s also necessary to remove food residues and dead leaves to prevent ammonia buildup.

You should also monitor water parameters constantly to prevent imbalances and make sure that the system is thriving.

Conclusion

Overall, I would say it is possible to keep an unfiltered tank, but it’s by no means easy. And it comports more uncertainty compared to a properly filtered environment. If you can, get a filter. The alternative, as you can see, is time-consuming and is open to fluctuations and uncertainties, which you may not always foresee.

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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