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An Overview of Self-Cleaning Aquariums by Meredith Clawson


Our latest article submission is from Meredith Clawson, one of our patron members. In her article, she discusses her experiences with maintaining a "no water change" goldfish aquarium, and how the key to her success is the natural removal of nitrates through the growth of aquatic plants in her heavily-planted aquarium. In addition to the plants, she uses a deep substrate and a low flow HOB type filter which may further support denitrification through the processes of anaerobic denitrifying bacteria. For anyone who has researched this topic on their own, you might realize that this is a HOTLY debated topic in other forums. Before we dive into this topic, I wish to remind everyone to be polite and respectful and not argumentative. There is no single best way to maintain an aquarium, and whether one chooses to do water changes or not, the role of natural denitrification processes should be considered when trying to optimize water quality and stability, and minimize labor and unnecessary water use. We look forward to hearing from other members who might be willing to share their own experiences.

This article is by no means a detailed how-to post, but rather a brief (sort of) introductory big picture of the no water change, nutrient-recycling fish tank system, which can be called the self-cleaning aquarium or naturalistic aquarium. It touches on the benefits to the both fish and the fishkeeper in general. The goal of this post is to shed some more light on the topic for those who might consider exploring alternative methods of fishkeeping, perhaps answering some questions along the way. So without further ado, let’s dive into it!

Judging from the social media posts and forum discussions floating around on the internet, it is probably pretty safe to say that the concept of a self-cleaning aquarium or no-water change aquarium is generally viewed as an elusive and mysterious one to most fishkeepers, considered more of a fantasy or an anomaly among the thousands of fish aquariums out there and potentially dangerous, thus probably not worth pursuing. It was to me for many years as well. The no-water change, natural aquarium, mostly closed ecosystem is not new and has only recently been receiving more of the attention it deserves on a number of YouTube channels and online platforms. As a challenge to the status quo, it has met with considerable controversy, by and large from those who have not tried such a method or who have tried and failed. I am here to say that the natural self-cleaning aquarium, when set up correctly, is by no means harmful to either the fish or fishkeeper. However, it to be tailored somewhat to the particular needs of goldfish, which has been my objective since I began keeping goldfish a number of years ago. But this is not difficult, though it involved quite a bit of trial and error in my experience.

For me, a self-cleaning aquarium teeming with aquatic plant life and healthy fish is the essence of the hobby and a dream that I chased throughout my entire fishkeeping journey. And at this point in my life, if I couldn’t keep fish in this manner, I probably wouldn’t keep them at all, because after experiencing the benefits of such aquariums, I never want to go back to how things were for me before. After extensive research and personally setting up dozens of aquariums and testing many setups, I have found that the methodology of a self-cleaning aquarium is one that can be not only accomplished and realized one time, but relatively reliably over and over again. It is one that affords beauty, simplicity, instruction, relaxation and balance; an enhancement to life rather than a burden on it.

My philosophy is self-cleaning tanks can reduce stress on fish, which inadvertently reduces your stress. It has been my experience that stress on fish is reduced by ample plant coverage and stable water conditions. Natural aquariums of this mode allow the fish the enrichment of living in a more natural habitat, fosters excellent plant growth, which in turn purifies the water and establishes a strong aquarium microbiome, so to speak. Live, healthy, growing plants do not only lend beauty and coverage to the fish inside, but oxygenate and purify the water as they feed off of the waste products from the fish. But plants even go beyond this; it has been shown that disease-inhibiting organisms use the surfaces of plants to colonize and become microscopic water filters, consuming pathogens that can cause disease. I attribute this in a large part to the longstanding good health of my fish kept inside such a tank, despite having no water changes for years on end. In the average sterile indoor aquarium with artificial decorations and minimal or no substrate, (perhaps combined with a lack of fresh water), recurring bacterial-induced disease outbreaks can be a nagging or even deadly problem. The scale seems to be tipped towards fostering bad bacteria in such setups, which is why many of the more advanced fishkeepers try to combat this problem in their no-water change tanks with a UV sterilizer. It is my opinion that UV sterilizers have their place (such as combatting a green water outbreak) but it isn’t a permanent one in my tanks. Instead of killing bad bacteria or continually trying to reduce their numbers, I want to outcompete them with good ones and build fish that are resilient. I do not rely on new, fresh water replacing the old to keep bad microorganisms to a minimum. I prefer to think of it like the water itself is part of the microbiome of the aquarium, full of beneficial components for the fish, and foster substrates and plants teeming with them.

In turn, fish that are less stressed means a fishkeeper that is less stressed. I was at a fish store the other day and happened to overhear the conversation of a husband and wife who were there looking for a well-known treatment for their sick fish, which treatment was out of stock at the store. I could tell by their almost frantic tones of voice as they paced up and down the same isle searching for it that they were not enjoying the situation. If you have kept fish for any length of time, it is likely you have experienced similar feelings of distress on your pet’s behalf at some point. This is a reality, but it is one that based on my experience I want to minimize, and I attempt to do that by laying a good foundation for my fish to flourish. Goldfish, especially fancy ones, are in many ways delicate creatures. (The aquarium is a delicate thing, too.) To thrive, they do best under conditions of stability and with a strong foundation of good water quality, good oxygen and good bacteria to support their health. As much as we can optimize those conditions to their advantage, we will reduce the stress on our fish and on us as a consequence. This brings delight to our hobby. Sadly, the aquarium hobby has a high turnover. I think the last statistic I read on the topic was that over half of fishkeepers give up within a year. If so, that means not very many people stay around long enough to reap the full benefits of being a fishkeeper, much less watch their children grow up along with their aquarium over the years. I can’t pretend to know all the reasons, and I’m sure diseased livestock is near the top of the list, but I can’t help but think that perhaps at least some part of that high turnover rate is due to how the average tank is not set up to be self-sustaining in the short or long-term. After all, this directly impacts the workload on the hobbyists and, at least to some degree, indirectly impacts the stress levels and health of the fish. Not only are sick fish a stress to the hobbyist, but the burden of regularly maintaining and caring for the average aquarium is something that many people struggle to bear depending on their life situation. It is one that businesses will usually hire out to a dedicated aquarium maintenance service, because intentionally or not, the tank was set up to be dependent on those services to begin with. Forgetting to keep up with the often time-consuming maintenance required for most aquariums today can prove detrimental and even fatal to the fish in the long run, and not everyone can afford to or would even want to call upon professional services every week to care for their home or workplace tank. This makes the concept of a self-sustaining setup more attractive, at least to me.

One of the first questions that comes to mind on the topic of a tank with no water changes is, how do you deal with the nitrates? There is little solid evidence to examine. I can only speak based on my personal observations and anecdotal findings of those I have learned from. While the subject of denitrification is complex and deserves an article of its own, my experience in fishkeeping over the years has lead me to theorize that nitrate is the final step in the nitrogen cycle that most aquariums nowadays never truly complete, leaving the fishkeeper trapped in a drawn-out version of new tank syndrome that continues for as long as they keep the aquarium. And the primary reason that they cannot simply stop changing the water and let nature take its course is because, in many cases, nature has been replaced by fancy equipment. The very equipment that is often believed (and effectively marketed) to reduce maintenance and make things simpler is, in my opinion, many times the equipment that burdens the aquarist with complexities in setup, operation and a demanding maintenance routine. What is commonly called “biological filtration,” a component of “cycled” aquarium filters, is intended to eliminate ammonia and nitrite and convert these into nitrate: but that’s usually as far as it gets. As the filter processes waste, more and more nitrates are produced, resulting in higher and higher levels of this byproduct.

But the impacts do not stop at the fishkeeper; they extend to the aquarium’s inhabitants! Another detriment that comes as part and parcel with their functionality is their effect on the water current in the tank. For fancy goldfish, I have found that stiller water is most preferable, but this could be expanded into another topic entirely. Suffice it to say that fishkeeping today is far different than it was thousands of years ago, or for that matter, even hundreds of years, and it was not until I started to explore the possibilities of natural fishkeeping methods, both historic and modern, that I began to question the current status of fishkeeping as we know it.

I would like to interject a note that it has been my findings that in some uncommon cases, nitrogen reduction has been achieved and a system balanced in a tank that is not naturalistic, but seldom without intentional intervention on the part of the fishkeeper in the form of supplying areas for anaerobic bacteria growth, in addition to accounting for some kind of buffering, and rarely without the addition of live plants in some form, much less in a bare bottom tank without extensive electrical equipment. Again, these results usually require a conscious effort to contrive and seem relatively sporadic in their effects.

Image shows, low-flow hang-on-back filter with well-seasoned media

Given the high cost of fancy equipment, the likelihood of experiencing a power outage at least some time in the winter in my area, the small and large scale environmental impact as a result of the plastics and microplastics involved in the manufacture of gear, and of course the general consideration for the happiness of the fish themselves, my journey in fishkeeping overall has greatly evolved from being highly dependent on buying and installing a contraption for every problem, to upholding a more minimalist approach when it comes to equipment and seeking natural solutions, where possible, that are in more harmony with the fish. For example, my 20 gallon office aquarium houses 3 fancy goldfish, a betta, two bristlenose plecos and a myriad of snails... and has never had any issues with water quality in any of the years it has been going. This would is considered massively overstocked by today’s school of thought and probably impossible to maintain either the health of the fish or the water quality. The extent of the electric I run is a small heater set to 73F (winter is cold here; this may be omitted in a more temperate climate), a full spectrum light suspended from the ceiling, and a small hang on-the-back-filter rated for a 10 gallon tank with the flow reduced nearly to a drip. There was a time when I would never have thought three pieces of equipment could sustain such a heavily stocked (by today’s common line of thought) 20 gallon for years, with no water changes, healthy inhabitants and perfect parameters! Now I can more comfortably consider the idea of a power failure, as well as breathe a sigh of relief at the thought of not ever having to lug buckets of dirty water outdoors every week, grit my teeth while wrestling to get the lid off a canister filter that is pouring water all over the floor, disassemble a UV sterilizer to try to get the water to keep flowing, or contrive yet another complex and unattractive DIY filtration build (although I must admit I enjoy doing that once in a while for other projects). In maintaining my fish tanks, my regular duties consist of two things: feeding the fish daily and trimming the plants every other week, at which time I top off the water evaporation. I do also like to clean the outside of the glass occasionally to remove any water spots. There are times when I am remiss and the plants grow a bit too much, but there is not much inconvenience to the fish in that until it begins restricting their areas to swim, at which point it becomes absolutely necessary to perform said trim.

Like my other self-cleaning systems, my humble 20 gallon aquarium brings me delight, because every day I look over and see the fish happily swimming about in front of a lush green backdrop and carpet, engaging with their environment. It is a decoration in the room that adds interest and life. (Back in my early days of fishkeeping, I would have been up in arms over the idea of fish being a decoration, but the fact is they are called ornamental fish for a reason!) The aquarium is an ornament of beauty, with the most beautiful part of it being the fish inside. We wouldn’t keep fish if we couldn’t view them, and that is probably the greatest pleasure of a naturalistic aquarium: viewing the beautiful healthy fish inside of the wonderful environment they are in, watching them interact with their little world as we go about ours. Of course, the fish are more than ornaments to us, they are our pets. We care for them and have responsibilities to do our best for them. Part of this responsibility to me for this tank is ensuring the fish are living the best quality of life that they can live, a quality of life that is not necessarily about having an outrageous number of gallons, but providing the most for them in whatever living space is theirs, larger or smaller, and enjoying all the benefits of a natural tank.

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