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Jack Heathcote learnt a thing or two about tankbusters from owning one of the largest private aquarium in Britain. Here he offers some thoughts for those considering their own.

When you choose a pet, it almost certainly hasn’t chosen you. It has been forced into your possession. Its fate is completely in your hands and you control its quality of life. The scope of your capabilities define the animal’s future. These capabilities might encompass knowledge, wealth, attitude, space, planning, and time, to name but a few. 

From the offset, there are ethical considerations, as with any pet. Firstly, do you intend to keep your animal for the duration of its natural life (and if not, why not)? Secondly, and perhaps more important, are you willing and able to ensure a decent quality of life until death do you part? If the answer to either of these is ‘no’, then perhaps you should reconsider pet ownership.

As an analogy, consider a dog. Would you keep a Great Dane in a tiny bedsit, where the nearest open space for dogs was an hour’s walk away? I daresay that you wouldn’t, and even if you tried to, the RSPCA would soon be on your case. Yet examples just like this (and often worse) are forever playing out across the UK, with those forgotten ectothermic vertebrates — the fishes. 

A healthy young Red-tailed catfish with swimming space. 

Why are people buying them? 

Taken on its own, a lack of space is rarely the reason that fish in tanks die prematurely. Typically, it’s stress and disease, power cuts and equipment failure, incorrect water chemistry, bullying and predation, or (mostly) water quality issues. 

However, assuming that a fish manages to survive through all of these many perils, the final hurdle will, ultimately, be space. And no excuse can be made for providing inadequately sized accommodation. But with that in mind, we have to grapple the complexities of what can be considered a large enough home for a given species, and how opinions vary over this. It can all be quite complex: for example, a reasonably sized active swimmer such as a Silver dollar, Metynnis hypsauchen, may require a similar sized aquarium as an African lungfish, Protopterus annectens, a species many times the Silver dollar’s size. 

Why are so many fish within the UK are being kept in woefully undersized accommodation? You’d expect the go-to answer to be a lack of hobbyist awareness. Historically speaking, that has been the case, with the majority of fish that have outgrown their quarters being the result of an aquarist purchasing a species without knowing it’s eventual size (followed by the aquarist struggling to quickly rehome it once the mistake has been realised). 

In the information dearth of thirty or more years ago, and at a time when even a seller may have been unaware of the sizes their fish grew to (or perhaps knowing the size but lacking any scruples to tell the customer), some of this blame could have been laid at the door of store owners and their staff. Aquarists of that time were often reliant on retailers for the bulk of their care information, including adult sizes.

But that was then. Nowadays, the vast majority of dealers are taking a far more ethical stance (especially in the wake of the Big Fish Campaign), and I’m unaware of any examples of a tankbuster being deliberately sold to an unwitting customer during the past decade. Quite the contrary, in fact; I often hear dealers interrogating potential buyers before they’ll sell them a baby monster.

There has been something of a groundswell movement in recent years, championed by the paying public and amplified through social media, encouraging retailers to not import tank-busting fish, but is that enough? Perhaps equal onus should be put on the customer to not encourage demand. 

Equally, with the near universal access of the internet via our mobile phones, there’s no longer an excuse for any consumer not to research the fish they’re aiming to purchase — even the most cursory search should send up any red flags associated with it. The ultimate size will soon be revealed even if you’re only browsing a search engine’s images. 

A good sized Pacu can reach dome 30g.

The complicit purchase

Let’s move on to the other, more sinister side of the story where greed, desire, self-gratification, and disregard
move in and morality, scruples and compassion take a back seat. This shadowy corner of fishkeeping is a sad reality of the 2020s. Someone sees a fish, or knows of a fish, or has heard of the reputation of a fish, and they have to have it, no matter what. 

Aquarists in this camp typically know the fish’s eventual size, but refuse to be deterred. They’ll all too often know that they won’t be able to provide suitable long-term accommodation, but don’t let this put them off, even if it means lying to the staff at the aquarium shop. 

A subgenre of this phenomenon includes those that kid themselves into believing that they’ll get a bigger tank as the fish grows. Unfortunately, it’s often the case that these individuals have neither the finances nor the physical space to live out this ambition. Monetary distractions may appear along the way — a child, a new boiler for the house, unforeseen and expensive car repairs, the loss of a job — and the fish are pushed into second place. 

There’s no tangible data on this, but though my experiences within fishkeeping circles I’d make an educated guess that nowadays the ‘must haves’ likely make up the ownership of some two-thirds of all inadequately housed fish (if personal testimony and multiple social media channels offer a clear reflection of the hobby, at least). 

I have also noticed to my horror the proliferation of digital forums and groups that deal with large or predatory fish, with a majority of members endlessly sharing photos of their behemoths in dinky aquaria. Nobody on these forums seems to bat an eyelid.

Jack's former tankbuster menagerie.

Size matters 

There are those who consider a tank of 180x60x60cm (a ‘classic’ 6x2x2ft) to be huge. In context, that’s around 650 litres of water — during light flooding, you’ll have likely driven through more voluminous puddles
in your car. 650 litres make for a very small pond that might naturally occur, and in the wild you’d be surprised if you found Sticklebacks inhabiting this volume of water, never mind an aquarium giant. Giant fish tend to inhabit giant waterways.

In decades past, a 180x60x60cm/ 6x2x2ft aquarium, the big tank of yesteryear, was owned by relatively few and was considered the right size of tank required to house an Arowana, or a Giant gourami or even a Red-tailed catfish. Today most ‘in the know’ aquarists would recommend a bare minimum of a 300x90x75cm/10x3x2.5ft tank for an Arowana or a Red-tailed catfish, and an 240x75x75cm/ 8x2.5x2.5ft for a Giant gourami, and a strong case can be made that these are still far too small.

 To throw in a wildcard, there are some tankbusters that don’t require such large dwellings, such as the previously mentioned African lungfish, Protopterus annectens. While this species can reach around 80cm in aquaria (perhaps slightly larger in the wild), its sedentary nature means that it would be reasonably comfortable in a tank with a minimum footprint of 210x75cm/7x2.5ft.

Then you have the Pacu, Colossoma macropomum, the adults of which can be double the weight of the lungfish — a good size Pacu can easily reach 30kg. These shouldn’t be considered for anything less than 360x120x90cm/12x4x3ft. For argument’s sake picture making a tank this size from glass. This requires glass with a minimum 15mm thickness — at these sizes, we’re looking at back-breaking weights, which are upwards of five and a half tonnes when full. That’s a lot of weight, a lot of space and a lot of money, not to mention the ongoing maintenance costs. Are you honestly factoring this in when you’re buying a cute little Pacu in a store? 

The 'lucky' tankbusters may end up rehomed.

To have or have not? 

I can offer many words of caution to the ‘must have’ aquarists, from what I’ve seen play out again and again. If you insist on keeping aquarium giants then there are a few things to look forward to.

Firstly, you’ll become increasingly aware that your fish is getting too big for its tank. It swims a short distance, turns and swims back, just as you might pace a small room in frustration. Friends and family start to point out that the fish needs a bigger tank. It feels like a personal attack, because it is. 

You try feeding less, but now you have a ravenous, undernourished fish which is growing slowly. Later, but much sooner than you’d hoped, the fish becomes obviously uncomfortable, possibly struggling to turn. You find yourself giving in and start to advertise the fish on the web for quite a hefty sum — after all, if you paid £10 for a juvenile, it must be worth ten times that now, right?

You soon realise you’ll need to lower the price, and not long after that you’ll try giving the fish away for free. But by now it has grown noticeably misshapen and seems to have a disproportionately large head, and you are desperate to get rid. You try every aquarium shop, website and public aquarium to no avail. 

Later the whole tank and its inhabitants become an embarrassing eyesore which you wish didn’t exist. The fish’s gills have now grotesquely curled, its body is badly disfigured, with a curved spine. 

At this stage, what you have is little more than a glass torture chamber. Your friends and family talk about it and you behind your back — believe me this happens. At this point even the RSPCA may reluctantly get involved (not that they’ll be able to take the fish). 

Finally, having reached the end of your tether, you get up one morning and remove the fish from the tank, take it somewhere out of sight and hit it with a spade. Is this a fair ending for a creature that was taken as a juvenile from the Amazon, and entrusted to you to live in a glass box? This may all seem like some embellished exaggeration but I promise you it is not. It happens.

Goliath tiger fish.

What to do? 

If you cannot provide long-term care for a sizeable fish then choose something else. Rather than browsing fish, finding one you like and hoping it will fit, try to reverse engineer the situation; look at the tank you have (or can realistically afford) and then assess which fish can live inside it. While there’s something awe inspiring about seeing a large trophy fish in captivity, a beautiful or interesting but manageable fish can be equally pleasing. 

A happy fish should be your aim. There are around 34,000 known species of fish, which means that there are plenty of appropriately sized choices for your setup, no matter how particular you are. 

To finish, I’ll point out a mistake of my own. Despite having scratch-built a 22,000-litre aquarium, which held tank busters for around fifteen years, a breakdown, job loss, and breakup with a partner combined with a battle with my electricity company (they had been charging me incorrectly for ten years), meant that I could no longer care for my fish. 

I was fortunate that, due to the large quarters, all of my fish were in great condition and all went to suitable homes, but even rehousing took nearly a year. Sizeable accommodation isn’t the only limiting factor, but everything involved with running it. It may be worth contemplating what life may throw at you, and what contingencies you have in place — I wish I had. You too may find yourself in an unprecedented situation which your fish get dragged into, as did mine. 

Clown knifefish can reach 100cm.

Won’t my fish grow to the size of the tank?

In a nutshell, yes and no. A fish in too small a tank can become severely stunted, but it will also be incredibly unhealthy. Denied the space to swim and exercise, a fish will reduce the amount of the growth hormone somatotropin that it produces. However, an inactive fish will start to develop dangerous fatty deposits around its vital organs. 

On top of that, the fish becomes stressed as it runs out of space, and stress results in the production of cortisol. Cortisol releases glucose into the fish, lowering immune systems and stifling somatotropin production even further. Combined with ammonia salts building up in the overloaded aquarium, the immune system is pressured even more, growth of the fish is drastically reduced, fat deposits accelerate, and the fish is locked in a perpetual hell. 

So yes, it will grow to the size of the tank, to an extent. But if it does so, you can hardly boast about that, given the litany of accompanying ailments. But then again, it’ll usually die of neglect beforehand.