You don’t have any fish in your aquarium, just plants. That means you don’t need a filter, right? Here’s why you may want to add a filter to your planted tank.

If you are an experienced aquarium hobbyist, you undoubtedly understand the importance of having a high-quality filtration system installed in your tank. Having a filter is essential for maintaining high water quality because it removes harmful substances from the tank water and helps to keep oxygen levels high for your fish. If these are the main things a filter does, however, you may be wondering if the live plants in your tank will be enough.


What do Plants Do in the Aquarium?

Not only can live plants enhance the appearance of your aquarium, but they provide several very important benefits as well. Live aquarium plants go through the process of photosynthesis during the day (or when your tank lights are turned on) in order to grow. They absorb carbon dioxide from your tank water (this is produced by your fish as a byproduct of respiration) and they use light as energy to convert that carbon dioxide into oxygen. Live plants also extract 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.


Do I Need a Tank Filter?


To summarize the information from the last section, live aquarium plants filter harmful substances from the tank water and convert carbon dioxide into oxygen. Given this information, you might be wondering what makes live plants different from any aquarium filter. After all, they seem to perform the same functions. So, do you really need to use a filter in your planted tank? The answer to this question will be different depending on several factors including tank size, the number of plants you have, and the number and type of aquarium inhabitants you are cultivating.


You can’t add one or two plants to your freshwater aquarium and expect it to be an adequate replacement for your filter. If you have a large tank or a large number of tank inhabitants, the ability of those few plants to filter out toxins and to produce oxygen will probably not be enough to keep up with the biological load of your tank. If, on the other hand, you have a moderately sized tank filled with a large number of live plants and you only have a few fish, those plants might be able to keep up with the production of waste and carbon dioxide your fish are responsible for.


The problem is that you will not really know if your planted tank can thrive without a filter unless you try it. Remember, it is essential that you cycle your tank before you add any fish or other tank inhabitants – this is still true for the planted tank. Having a filter installed while your tank is cycling can be beneficial, especially because you want the water quality to be high when you add your fish. It isn’t a bad idea, then, to start your planted tank with a filter and to keep adding more plants until your filter becomes unnecessary. Just make sure that you have another means of cultivating biological bacteria in your tank to maintain the nitrogen cycle once you remove the filter. You can try installing a sponge filter or simply let the bacteria grow on tank surfaces.


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 certain keep a planted tank without a filter.

The funny thing is I was just thinking about this. I am planning on moving in the near future. Since I would have to recycle my tank, I was thinking about adopting my fish out. Then maybe doing an invert only tank. I was wondering if a filter like the cascade 700 I have is needed. It is good to know that it might not be.

Thanks for the great advice.

I am new and set up a tank using miraclre grow, water wisteria, and sand/rocks from my creek, and that's it. The wisteria is growing really well (actually too fast), and even though the water and the tank doesn't look crystal clear some pond snails are doing good. I need to figure out how to make a siphon or gravel vac because there is snail poop and random detritus covering the ground on the side that has nothing yet. I don't plan on buying a filter until after Christmas and when I add in shrimp.

You will probably need a powerhead to circulate the water. I had an outdoor tank with plants and no livestock with a small internal filter and had green water. As soon as I put in a HOB, the green water went away. The HOB had nothing special in terms of media, just two pieces of 35PPI sponge.

Actually as an experienced fish keeper I fully realize I don't in fact need any filtration at all. In fact even with fish, in a lush, planted tank I still don't need a filter.

Your statement makes it sound like you need tech in almost all instances. I fully disagree and in fact have a thread in the journal of a 29 I had for a period of time that ran exactly as I describe. When I was just starting out in the 70s a woman I knew had multiple tanks, some planted some fish only but none had filtration. They ran successfully for years. But they didn't just run. They thrived.

So no. You don't need tech. You need common sense.

I still have one or two tanks with no filter. And my breeder tanks are super high tech filter systems. I bought 20 corner box filters and run them with filter floss. They all run on a central air system. One breeder tank even is running with an air power HOB filter I bought 30 years ago.

I've got a 55 outside on the porch to the fish house. No filter . No water changes. Right now it's evaporated half the water. I may change the water this weekend. Might not. But it is still going with no fish loss for over a year.

I use to run a heavily planted tank with only an air stone.
It ran nearly 2 years with green mollies and ghost shrimp before I had to tear it down and move.

The real answer is it all depends on how many plants, how many fish, and how much water.

If the plants nutrient needs are higher than the bioload and there is enough circulation for gas exchange then you essentially have a glass pond.
No need for filters in a well planned pond.

You are correct regarding a well planned pond. Difference is in nature a "well planned pond" is one in which nature has created an equilibrium.

There are days in which I would like to go this route LOL. General maintenance can suck after awhile. But, I do like where my tank is headed so I do what is needed.

And to be fair my old "glass pond" was full of Bacopa Caroliniana and Water Sprite.

It was a 55 natural dirted with a dozen or so ghost shrimp and 5 green mollies (all male)
It was about as low tech as you can get, lol

100% agree!

Most filters add to the water volume, catch the larger particles, and circulate the water in the tank. This can be done with a simple sponge filter and an air pump.

Water quality goes beyond just filters and often involves human intervention like doing water changes and monitoring water parameters for fish tanks to stay in equilibrium. As was said bio load, plant mass, types of plants you have, gas exchange rates, water volume, light and CO2 levels, and bacteria levels all effect this equilibrium and how much intervention is needed. I have no doubt that a tank can be kept without a filter system especially on larger tanks but in general filters only help with all of those things listed above. Some will cite maintenance as a con but when I think of all the gunk that I remove during a 3 month service, I'm glade that I can easily remove it and start with a fresh filter. Filters also significantly improve the bacteria levels for the tank increasing the chances that water quality will remain very good.

https://www.youtube.com/watch?v=psGQf2rT49w


not only is it possible to keep a full fw aquarium (balanced bioload as mentioned above post) without a filter, even a sponge filter, its possible to keep a reef aquarium just the same with only its natural substrate inclusions as the filters (active surface area)

going further, both can be kept still, without circulation if required (handy in small tanks to avoid wiring and clutter) and as mentioned above water changes come into play and keeper work to export waste as needed. balanced bioloading slows the waste incursion compared to typical tanks.

if the setup runs a few weeks and is overtaken by algae, or goes rotten, that will reinforce the old school ways of playing within the rules due to care methods lacking.
but if the exact same life forms are supported long term in tweaked systems, carefully balanced, then lifespan of the tank and biomass production becomes the justifying factors. people who want to experiment with pure filterless tanks will usually google a while before starting, and in that action you'll find the places its being documented in high res pics and vid. youtube has plenty for searching filterless reefs and planted tanks.



changing understanding of tank biology is literally reversing the rules in some tank designs to allow for simplicity. some examples are very old very long running systems to back up the method. if anyone was curious about the stilled, non circ reef aquariums just google pjreefs jar or visit the biotope forum at nano-reef.com and theres even a few ulfiltered micro reefs littered on this site


fish are not sentenced to death in the micro tank above. he's in there eating pods out of the water so a hundred little white bugs aren't flitting around the tank (common for shrimpers)

as of now, is replaced today by fry. a cycle in and out
the tank is stilled, noncirc, no filter and is also sealed with a special lid that prevents evaporation, but can still be raised for work

the focus of the video is the oxygenation levels of the water

When I started on this hobby aquarium gadgets - air-pumps, heaters, filters, etc - were unavailable to me, and even fish food was what I prepared myself. When I grew up and moved away, I lived in places where there was neither electricity nor running water. I carried my hobby with me. My tanks were lighted by natural daylight, sparsely populated with fishes, and heavily planted but sans any aquarium gadget. For much more than 20 years the only way I could maintain a tank was by growing the plants in them and an occasional water change - the fertiliser was from the choice of substrate which had to be changed every 3/4 years. It was fun.

When I came back to urbanised area - the world had changed a lot - I had much to learn including the progress made in the hobby and all the new gadgets being used. I tried to adapt to the new ways but was constrained by equipments which were still mostly unavailable but with the ideas and knowledge I picked up and my DIY skills - I could keep more fishes in my tank. That was fun too.

Then I did not really go all the way to ape the modern ways except as an experiment to see what was possible. My unique way of tank-keeping is fun too.

I have Planted tanks that do not have a filter; usually they are very heavily planted. Plants absorb the nitrates, so actually you can get away with only topping off the water in the tank instead of doing water changes. Usually the filter serves the purpose of circulating water within the tank. This has a lot of benefits and keeps plants healthy. So even if you do not use a filter it is better to use a power head to circulate the water in the tank.

I fully agree that you don't always need a filter. The below is my 2 cup aquarium, and it only has snails and Dwarf Hairgrass in it. It's doing fine.

Attached Thumbnails

 

Well, filters do more than just filter.... they also help with circulation.
I.e. all the water gets a turn to do gas exchange with the surface for example.
Also it helps prevents low oxygen environments at the bottom (less of a worry in a 2 cup tank , and helps redistribute hormones away from the floor where it may cause carpet plants to stretch...

plants grown without a current are weak like terrestrial plants grown without wind.

there are many things we don't need that makes life easier/better. Can openers, toilet paper, tv remotes....