Are self cleaning fish tanks still fiction?
Does the idea of never having to carry out a water change ever again appeal to you? Nathan Hill considers how close we really are to maintenance-free fishkeeping.
There are a few concepts that tease aquarists. Converting a marine fish's physiology to that of freshwater, for example. Imagine the riches that await whoever can breed a guppy sized, freshwater clownfish. That particular act of genetic wizardry (not to mention the ethical backflips needed beforehand) could make the inventor richer than the film makers who put Nemo-fever in to the general public in the first place.
The closest I see aquarium innovations coming to being outright alchemy is when it comes to self-sustaining/self-maintaining/maintenance-free/self-cleaning (delete as applicable) aquaria. That curious transubstantiation of glass and water into an autonomous entity seems to be the holy grail of tank developers the world over.
For the best part, these efforts are noble. If the goal is to remove all possibility of human error and to create an ideal habitat for livestock, then I'm all for it. But if the objective is to pander to the laziness of potential buyers, then that's not quite as well-intended.
Reducing or removing maintenance is by no means a new concept. Some major aquatic brands have tried over the years, introducing pollutant guzzling pellets and potions, and bacterial cultures to convert nitrates and phosphates, to more recent dabblings with aquaponics systems – using plants as a means to harvest out pollutants.
Let's face it, many of us loathe a water change. Some of us do have our ulterior motives to getting our hands wet, though we are few. Along with many in the aquascaping community, I find something incredibly therapeutic about trimming back plants once a week, reshaping growth and then performing a precision syphon. It gives me a chance to refresh the tank, but also to wipe the slate clean; before starting another weekly course of fertilisers, I like to know that I'm working on a blank canvas, chemistry wise.
But aquascapers are pretty unique in enjoying this labour. For others, tank maintenance is something that causes the lower back to ache, gets sleeves wet, stresses the fish, and results in water sloshing about all over the carpet. Then there are the delicious smells of biofilm and sludge from the filter, the inevitable 'aquarist belly' if you happen to take just a momentary slip from good hygiene, the uprooted plants that just won't go back down, and that tedious little patch of algae down in the corner that decides to reveal itself just after you think you've got everything finished.
For more reckless aquarists, there is the risk of electric shock, a broken heater, or a pump running dry during the exercise. It is easy to see why for some, getting in to a tank is as daunting as performing open heart surgery. For most of us, I can see why a maintenance free tank holds its appeal.
Wide of the mark, or wrong audience?
The idea of a self maintaining tank has a few inherent problems. The idea of a standalone system that never needs any kind of input runs the risk of relegating such a tank to the status of a commodity. An ornament, if you will. Now that might sound uncannily close to the de facto role of aquariums in general, but I strongly suspect that the telling difference here is the input on the part of the aquarist.
Let me use gardens as an analogy. We've all seen glorious gardens, I am sure. I have visited many, both private and public, usually in the role of a tourist. But it's one thing to just appreciate a nice garden, and it's another to have tended and nurtured that garden yourself. It is that role of stewardship, of caring for the garden that makes it inimitably intimate to the gardener. I can look at a garden and think of it as pretty, yet have no vested interest in its well being.
But in a garden of my own, where my prize flowers are being gobbled by aphids, I will be quick to rectify the problem. I become emotionally invested in the garden. I think the same applies to many fishkeepers. Many of us will have experienced poorly fish that we've brought back from the brink. Many of us will have fretted over an anomalous water test. This is all a part of the wider fishkeeping experience, and herein lies the difference between being a hobbyist and merely owning a fish. Our successes and interaction are the reward of the hobby, not just the visual aesthetic of having a tank on the shelf.
At the same time, I accept that very few people enter this game wanting a high maintenance, dedicated set up. Of course, ease of use is a wonderful selling point; I've made this point a hundred times before. But making the aquarium so interaction-free that it's just a glorified vase isn't going to inspire folks to move up to anything more substantial any time soon.
The other elephant sat in the room is the very concept of a totally maintenance free tank. I've come across similar propositions before. Hell, I see a good half dozen every year, all claiming to be the new, revolutionary way to keep hands-free aquaria in the home.
Where are we so far?
Looking at the options for a self sustaining tank, we can split roughly between a few camps. Firstly, there's a hermetically sealed unit. This would involve an airtight box to which nothing but light and heat can be added or subtracted. I think that NASA and National Geographic have put together something along this line, along with countless GCSE science classes around the world.
The theory is simple enough. A completely closed tank harbours the first strains of life, and the basic essential elements: carbon, nitrogen, etc., to sustain it. From there, the only energy source required is light, which then facilitates the growth of algae and cyanobacteria, which in turn create oxygen, which then allows aerobic bacteria to convert down dying algae, and so on. Some bright sparks have even managed to get this process so well encapsulated as to sustain the life cycles of tiny shrimps. But for a fish, this is presently inadequate. And let's be honest, if I'm still in control of the all-essential light levels, such a tank still isn't self sustaining. But at least it'll never have a rampant nitrate problem, as no source is ever being added to the tank. I'll never have to water change it, after all.
There are also closed but not sealed tanks. This is a system rather like the one above, but with the obvious difference of having a gas exchange at the top. So, oxygen can get in, and CO2 can get out. That might sound like a vast improvement, and it certainly helps to counter things like pH swings through excess carbonic acid build up, but it's still something of a time bomb. Think of this kind of tank as a bottle garden, which you just leave to its own devices: no water changes, no feeding, nothing. Like the tank above, there's not exactly going to be an issue with nitrates or phosphates, because there's no input. But without input, there's the problem of certain organic minerals depleting. Again, this would be a no go for fish. They are, I must confess, great fun if you want to set something up for a little Daphnia and other pond life, but that's about it. Mosses work really well in them, if that's your thing.
Then we have the sort of closed but open tanks, and the outright open tanks which make up the mainstay of offerings we see on sale to the public, and these warrant closer inspection.
In the semi closed tank, the key difference is the input of food. Such a tank will house fish, and rely on one of many different, often esoteric methods to control the production of waste. One method, of course, is to use filtration. But, as we aquarists know, that only gets us as far as a tank with slowly amassing levels of nitrates, phosphates and other potentially harmful metabolites produced through biological activity. In order to eradicate the need for water changes, either chemical resins (ion-exchange resins that swap, say, nitrate for something like sodium) or anaerobic filters might be considered. Anaerobic filters never really took off any time historically, because of their wildly unpredictable nature. Get the balance wrong, and you'll have a tank heaving with hydrogen sulphide and dead fish.
Even if you get it right, an anaerobic filter is usually too inefficient to have any ground breaking, long term impact. There are, I must cheerfully admit, several prospective nitrate and phosphate filters (just look at any modern reef tank to see an example) that utilise starches and other carbon sources, and these will be interesting to follow if they make any consequential jump to the freshwater hobby. However, nitrate and phosphate removers still don't remove other metabolites, nor do they replenish essential minerals needed for successful filtration. And the big crusher is that such resins need replacing, so suddenly any tank using them becomes far from maintenance free. So much for that approach.
Another method, which aquascapers would be quick to draw reference to, is the use of plants in controlling wastes. I've flagged this approach recently, drawing attention to the potential of aquaponics set ups with fish. Since writing that piece, I've had interesting feedback from both hobbyists and researchers, highlighting some of the ongoing issues they've had with a hydroponics system — specifically the decline of hardness and lowering of pH over time — but the basic proposition of fish consuming fish waste is salvageable if some of the kinks need a little ironing.
Plants are key players in ecosystems. The fix carbon, uptake nitrogen, create oxygen, and generally act as a bedrock for higher life. But what they aren't is foolproof. I've seen a few systems over the years that have incorporated what's known as the Walstad method – an aquarium ecosystem that relies on plants and soil to remove nutrients and provide minerals.
In fact, some of the healthiest tanks I have ever seen use the Walstad approach. Snakehead keeper Paul Jones relies on it in his own, spotless aquaria, running annual – yes, annual – water changes, and to this day I'm flabbergasted at how pristine his livestock is. But I do quickly add that his are quite large tanks, with a couple of snakeheads in each; stocking density was not what I'd call typical.
But take note, Paul still has to water change. That's maintenance right there. Unless I've misread her, even Diana Walstad doesn't claim that her method is entirely maintenance free or self sustaining: only that maintenance is reduced. Calcium and carbonates can deplete, pH can fluctuate, and without monitoring by the fishkeeper – water testing at a minimum – then the lives of the fish inside can be in jeopardy. So it's not looking great for this type of semi-closed tank to be maintenance free, either.
Aside some minor variations on the theme, the last option is what pretty much all of us do – an open system that relies on food going in, and water being replaced regularly. Essential minerals are replaced, wastes removed, and with a little monitoring and testing, we can tinker and tailor our chemistry to suit our fish. And to be curt about it, for the privilege of having live fish in our properties, I think that's an entirely fair payoff.
Hope for the future?
In a nutshell, we're no closer to the self-sustaining, maintenance-free fish-safe aquarium than we are to a perpetual motion device. The best fishy minds have been hammering away at it for years, and the accepted consensus is that it's still just out of reach. But then, we don't even understand all of the physical interactions in an every day aquarium. We still argue about the bacterial species involved in denitrification, we ignore the wealth of tiny protozoans and other microorganisms found in media and substrates, and we can't even reach an agreed consensus on the foolproof way to establish a biofilter.
For now, the appeal of a maintenance free tank is alive and well, and will likely snare the kind of buyer that doesn't really want to keep fish, but has some money burning a hole in his or her pocket.
With this in mind, are such set ups a step up from a bowl? You betcha, they are. The fact remains that there are those folks who don't 'get' fish but are going to try to keep one anyway, and if it's a toss up between something like a tank with some plants and a crude filter not getting water changes, or a barren bowl not getting water changes, then I'm reasonably confident which is the lesser of two evils.
That's not an endorsement, because I'd much rather it was the case that whoever was selling the tank took the time to explain the needs of the fish and encourage the buyer to leave with something way more substantial, along with a syphon and a test kit (or with nothing at all, if it came to it).
But until that happens, I guess I'm just going to have to sit politely as I watch a stream of hopeful designs take their place in history as the tanks that never quite lived up to the hype. I only wish that so many fish didn't have to suffer because of these optimistic attempts along the way.
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