Why do our fish sometimes die for no apparent reason? There can be many causes, explains Nathan Hill.
To try to catalogue every possible reason for an aquarium wipe-out is a colossal and unrealistic task, but, when I was a store manager in the trade, I saw more customers who had 'inexplicable' losses than I care to remember.
Having investigated tank crashes through a variety of reasons, I’m confident that addressing a few potential problem areas could reduce outbreaks of this phenomenon.
What are the factors? Some crashes are understood, like the alarmingly common 'new tank syndrome' where over-enthusiastic newcomers fail to appreciate the importance of the nitrogen cycle. Here, rapidly-accumulating wastes build to a point before ravaging the aquaria with deadly nitrogenous compounds
But what about 'mystery' crashes? What could account for sudden losses in a tank running successfully for many years, a tank regularly maintained with water quality frequently checked? Assuming absolute basics have been covered, that the heater and equipment are all satisfactory, assuming that ammonia and nitrite are nil (or negligible), there’s surely no reason for fish to just die?
Old tank syndrome
Many problems were down to what I call 'old tank syndrome' although this is as much 'old test kit syndrome' as well.
Old tank syndrome is characterised by a chronic problem suddenly becoming an acute problem which could be avoided with proper testing.
Most of us realise the importance of regular water changes. They help to reduce nitrate levels, as well as phosphates and other dissolved organics, and they help re-buffer essential minerals that deplete daily. Most of us will use a test kit to ascertain the frequency with which we should be doing these changes.
So how much faith do we put in them? Kits, especially off-the-shelf liquid reagent varieties, have a finite life span. The moment you open the bottle there’s a limited time before the contents start to oxidise, making them inaccurate. And what use is a stale nitrate test kit?
How many people this week alone gave themselves a pat on the back on observing a marvellous reading, 5-10ppm perhaps, when in reality that figure could be closer to 100ppm.
How can this cause a wipe-out? Apart from accumulating nitrates, we should also think about the build-up of acids within the tank.
One of the many by-products of nitrification is the release of hydrogen ions into the water by our 'good' bacteria.
These ions are a key player in making water acidic. Combine this build-up of acid with gradual erosion of buffering minerals not adequately replaced through lack of water changes, and the tank slides towards disaster, losing ever more stability until reaching a tipping point.
The pH crashes, livestock — already weakened by chronic exposure to nitrate — are also suddenly subject to severe acidosis. Without immediate action, death becomes inevitable.
Acute acidosis is easy to spot as the fish quite literally try to get out of the tank. They jump, dart, race from end to end, and die.
But this is only one eventuality of a useless test kit. For others, the tank may start to harbour anaerobic patches (areas that lack oxygen through combinations of excessive nutrients and poor water flow) and these may give rise to undesirable bacteria, facultative anaerobes which convert nitrate back into deadly nitrite, or give rise to hydrogen sulphide.
This is a nasty chemical and is detectable through a rotten egg smell (being responsible for much of the odour associated with flatulence), as well as leaving black staining on any areas the anaerobic bacteria grow. It’s an effective poison, destroying the ability for cells to respire and causing fish to suffocate internally.
Often, bubbles coming from the substrate will be little more than nitrogen, but don’t ever become complacent. And, if you start to see black staining on the underside of decor or substrate, sort out your husbandry.
Older tanks may inadvertently stress new additions, assuming these arrivals have come from a clean and healthy environment. New fish in a tank are often blamed for the introduction of diseases, but how many of these situations could have been avoided if the newcomers had not been subject to 'nitrate shock'?
Combine this with 'established' fish with immune systems suppressed by long periods of chronic nitrate exposure, and such situations are asking for trouble
Avoid these types of crash by not putting too much faith in one old, possibly stale, testing kit. Replace liquid kits periodically and, if a result looks too good to be true, it probably is.
Water hazards
Tapwater is not the best medium for fish, at least not in its most raw forms. Agreed, it’s packed with chlorine, but If it wasn’t we’d all be running around with cholera.
Nowadays, almost all proprietary dechlorinators tackle both chlorine and chloramine.
Be careful if trying to use a product that only deals with chlorine, as against chloramine it will be counterproductive, releasing toxic ammonia into the water. That’s assuming it even touches the chloramine. If it doesn’t you have a problem.
Chloramine poisoning is similar to carbon monoxide poisoning in humans. It destroys the ability of the blood to carry oxygen and fish struggle if they can’t breathe.
When dechlorinating, give the product time to take effect. Adding dechlorinator after the water has been put in is useless. Pre-mix it in a bucket and give it a good few minutes to work.
Water companies are regulated as to what they can and cannot put into our supplies, and will usually notify us of any work being undertaken with domestic supplies.
In the long run, watch out for the addition of fluoride to tapwater. This is already raising concerns in America where it is now accepted that levels of 1.5ppm can prove lethal to salmon. Worryingly, optimal levels for fluoride use are between 0.7 and 1.2ppm — very close to that danger mark.
Beware other uses!
I’m amazed at how many people use their water changing equipment for other chores — such as washing the car or cleaning windows. Cleaning products are riddled with surfactants like sodium laureth sulfate which is lethal to fish.
Just look at any water course into which a soap has been discharged. They are there because they adore attaching themselves to fat and oil — great for dirty dishes, but not living organisms. The amount of soap required to kill a fish is painfully small and can leave no trace in the tank.
Many use equipment specifically for the aquarium— and nothing else. But where does it live? You’ve done your change, poured the water down the bathroom sink, sat the bucket on the floor and gone for a cuppa. In the meantime the kids have jumped in the shower, shampoo flying everywhere, including into your bucket!
When you put it back under the tank two hours later, the suds are just a residue, sat patiently on the side…
This scenario may sound far-fetched, but I’ve seen it all too often. Always thoroughly rinse any tank equipment before and after use. And don’t store it next to your household cleaning products. Things splash and, when they do, you’ll only find out to your cost.
It goes without saying that you never wash anything that goes into the tank with soapy water, including your hands. Residue will sit with you for hours after you’ve done the washing up, so rinse those things before you plunge them in to reattach that pesky algae magnet.
Be wary of anything new in the tank, too. I can think of many cheap ornaments smothered in highly toxic lead paint. Not that these are specifically destined for aquaria, but you can bet that if there’s a quick buck to be made from their merchandising, they will find their way into tanks.
Inappropriate types of wood leach toxic resins, porous rocks are stored next to bleach in the back of a fish shop — all dying to crash your hobby.
Always avoid iron. That old anchor may look great, but it’s wreaking havoc as the ferric iron (rust) is happily oxidising fish tissues, tearing gills apart and generally giving everything anaemia.
Smells of danger
Certain advertisements make me shout obscenities, especially when they advocate stupidity. Whenever I see a commercial on TV with yet another air freshener on top of an aquarium, I cringe.
I estimate that contamination from extraneous (outside the aquarium) sources accounts for over half of all tank crashes in this country.
Chemicals, such as those found in some air fresheners, are lethal. Crank the dosage up and they’d kill us, too.
Look at the ingredients of an air freshening fragrance and you’ll see all manner of innocuous sounding chemicals.
Examine them more closely and you might be tempted to go smelly for the rest of your days…
Take just two from a well known brand of scent. One is linalool, a lovely smelling chemical, spicy and floral, not only found in air freshening products but also soaps, shampoos, lotions and so on. It’s also used by pest controllers to kill fleas and cockroaches.
Ever heard of coumarin? It’s a chemical that gives off a pleasant hay smell and is used in many fragrancing products. It can also be used as a highly potent rodenticide, causing internal haemorrhaging.
Too many aquarists are unaware of these hazards sitting inches from their tanks although, in fairness, these products often have a warning about toxicity toward fish in microscopic print somewhere on the package.
Airborne chemicals don’t stop with air fresheners. Nicotine from tobacco smoke is lethal to fish and incredibly hard to detect.
The lethal level for a mouse is a mere 3mg per kilo body weight, humans are far lower (as low as 0.5mg), and although fish are quite high by comparison (over 68mg for a goldfish) nicotine uptake through the gills behaves a little differently than through the lungs — not to mention the bioaccumulative nature of the tar.
To put that into perspective, the nicotine from one 'normal' strength cigarette could kill about five or six large mice. A large mouse weighs in at about sixty grams — and I’ll bet a guppy is lighter!
Insecticides are a guaranteed killer. One of the most commonly used is permethrin, which can be lethal to some fish at doses as low as 0.0018mg per litre. That’s tiny and it can be accumulative, having a half life of two and a half days in water and creating time to build up to lethal levels inside a fish.
Other sources
If it emits fumes or vapour, it will be dangerous to fish. And I’ve not even touched on paints, polish, joss sticks, glues, solvents, wood preservatives and the hundreds of other deadly chemicals in our homes.
Poisoning of this nature can be easy to spot. Expect fish to be incoherent, if even still alive, lying on the bottom and shimmying. A poisoned fish will often fail to react if you try to touch it —not that you should — and, strangely, a poisoned fish will often exhibit intense coloration, far brighter than usual.
Often symptoms can become apparent over a very short period, especially if the tank is using an air pump to increase oxygenation or water movement. Water is incredibly good at trapping suspended particles from the air.
The remedy depends on the type; chronic or acute. For acute poisoning, the fish need to be transferred immediately to a toxin-free environment. For chronic poisoning, all you can do is remove the cause and perform frequent, large water changes in the hope that fish have the strength to flush themselves through.
Prevention is better than cure. If it creates a scent, keep it away from the fish. If it can transport itself through the air, keep it away from the fish!
Bubble bobble
How many of us bring water up to the correct temperature when doing a water change? I’d like to think most of us do, as, although rare in causing a wholesale crash, dissolved gases can still play havoc in a newly changed tank.
We’ve all taken a glass of water to bed, freshly drawn from the tap and nice and cold. In the morning it will be full of small bubbles and taste differently. This is because, as water warms, it loses its ability to hold on to certain dissolved gases, chiefly nitrogen.
The same will happen if we pour cold, dissolved gas-rich water into our aquarium. It will warm and the gases will form tiny bubbles as they come out of saturation. If your fish have taken big breaths of this cold water the gas will form bubbles inside them, in a way not unlike nitrogen narcosis (the bends) in humans.
Before racing for that hot water tap, however, think about where that water’s coming from.
Many houses have huge copper tanks to store hot water, not to mention all the copper piping feeding from them— and you don’t want this metal building up in your tank, especially if keeping marines! If heating water before use try a small amount of water heated in a kettle, but be extremely careful how much you use. Boiling water can play havoc with the temporary hardness content.
Buy food wisely
It may seem economic sense to buy a huge pot of dried fish food — and some people can make a good-sized tub last over a year.
But this is not a sensible move. Not only will food lose its vitamin content, but ongoing moist exposure, such as wet fingers going back for a second pinch, may lead to aflatoxins which are by-products of mould growths and poisonous to fish.
Although unlikely to cause an overnight crash, aflatoxins will contribute as a chronic stress factor, weakening immune systems and making fish more susceptible to other influences.
How about plants? Retailers tend not to stack a range of plants safe for consumption. Certainly two plants I’ve started to see more and more of recently are Caltha palustrus and Lobelia cardinalis and both are toxic. Are you sure you want your Silver dollars munching on them?
Many harmless-looking foodstuffs may be harmful to fish.
I remember having many years ago some young Metynnis who just loved to eat seeds from my apple cores, but only later did I discover that these are riddled with amygdalin, a cyanide-producing compound that can even prove fatal to humans in high enough doses
Danger close at hand
So, danger lies around every corner of your home, at the bottom of every bucket, and in every pleasant-smelling scent inside your four walls. The tragedy is that most events that cause a wipe-out will never be discovered — the cause so innocent as to be totally unremembered.
So before shouting at your local dealer and accusing him of selling you the fish that wiped out your tank, think first. Was there anything harmful that could have got in to do the damage?
Is there something sitting harmlessly all this time, waiting to savage your livestock? If there is, and you find it, let others know. It would be a massive undertaking to try to list everything that could cause tank crashes — but in doing so we could all make the hobby a far more rewarding place.