It was all going so well......

It was all going so well.....

After you have steered your new aquarium through the shoals and sandbanks waiting to snare the inexperienced fish keeper, you can bob for a while in the calm lagoon beyond. Feet up on your footstool, glass in hand, you can spend your evenings surveying your balanced, healthy, attractive fish tank. Once all the initial problems are out of the way, so long as you keep on top of the weekly maintenance everything will be fine.. won't it?

Well, it probably will. But what is going on in a fish tank is far more complex than you probably like to think about. You may think that by the regular maintenance you are ensuring that everything stays the same in your little glass world. In fact you are just managing the changes in your system so that it doesn't change too far in any one direction. The fish excrete into the water, thus changing their environment - you change twenty percent of it, thus hopefully changing it back. The only way to keep a completely unchanging tank would be to sterilise it all and keep it in a vacuum. (And no fish either!).

By keeping an eagle eye on your tank you manage to keep all the changes within strict limits, but it is easy to forget that any breach of those limits can send the system out of control almost without warning. Water in the UK is, whatever Perrier would have you believe, extremely safe for people to drink. Unfortunately what is safe to drink is not necessarily the same as safe for fish to live in. Chlorine and chloramine levels can fluctuate heavily. If your water is usually fine to use without dechlorination, you can get into the habit of doing so. But the day the water company flushes chloramine through the system to make sure it's all squeaky clean will be the day you find all your fish inexplicably gasping their last. Check with your water company to see if they use chloramine. While chlorine can be removed by leaving water to stand and all proprietary dechlorinators, chloramine is more persistent and more unpleasant. Chloramine is a compound of chlorine and ammonia, and some dechlorinators just remove the chlorine, leaving water full of ammonia. If you pour that into the tank you will instantly overload the filters - you are effectively simulating massive overstocking. If your company uses chloramine, ever, always dechlorinate properly with a dechlorinator that removes both chlorine and chloramine.

Occasionally other stuff gets into the water, and a sudden case of poisoning can sometimes appear to be totally inexplicable. I once had an office aquarium, which was fully established and a source of pleasure to all the staff. We were not only upset but mystified when, one Thursday morning, all the fish were gasping at the surface when nothing had been changed. After several (warmed and dechlorinated) water changes and only a few fish lost, order appeared to have been re-established by the following Friday, only to have the same thing happen again the next week. Everyone was quizzed as to their Wednesday activities, but the cause remained a mystery. After several weeks of this, after which only a few hardy fish remained, the problem was solved by a particularly dedicated worker who was doing overtime when the cleaners came in late that night. It was found that Wednesday night was her night for giving the tank a good clean with furniture polish. Similar results can be obtained by painting and decorating in the room where the aquarium is, or by a hefty dose of fly spray in the summer. The fish tank is not a completely enclosed environment, and air pollutants that are only a mild annoyance to us, and quickly forgotten, can have lethal effects on your fish. Even air freshener is a toxin if sprayed too close.

Perversely, you can manage to poison your fish, as a friend of mine achieved, by being too conscientious on the cleaning front. After his tank had been running, uneventfully, for a year, he noticed that there was a bit of debris building up and decided that it was time for a spring clean. He took everything out of the tank and cleaned it carefully, making sure to use only his fish bucket (which had never been exposed to household cleaning agents) and boiling water. With everything shiny again he replaced it all, filled the tank with dechlorinated water, and waited for it to reach the correct temperature before replacing the fish. At first this was a great success. The fish were delighted and swam about with especial verve and enthusiasm. It took a few days before they started to get sick, to gasp at the surface and grow pale, and finally to die. Unfortunately the tank relied on an undergravel filter for filtration, which works by hosting a multitude of bacteria in the gravel that eat the fish excretions. After being boiled thoroughly, the gravel was not only sparkly clean visibly, but devoid of any remnant of bacteria. As the fish excreted, the toxins built up in the tank, and the water became poisonous. If you want to clean the gravel of an undergravel filter, do it in stages and clean a section each week, and a bit of filter booster culture will help mitigate any effects. If you want to clean the sponge of an internal biological filter, cut it into sections and change one section each week. Completely cleaning a biological filter renders it useless until the bacteria levels have built up again, by which time your fish population will be radically diminished.

Even if you don't do anything harmful, the situation in your tank is continually changing by the very fact of the fish living in it. In the normal course of events, healthy fish are likely to grow, and might spawn. It is easy to forget this factor, and assume everything is fine, until one grows that extra millimetre that tips the balance over the knife edge. The tank is now slightly overstocked, and poison levels begin to rise slowly. The toughest fish probably won't show much sign of it at this stage. Unless you consider the problem and stop it in its tracks, by reducing the number of fish or increasing the filtration, the pollution levels will continue to creep up until, apparently suddenly, all the fish start to become ill. Alternatively, if there is a weaker specimen, he may get sick before the others. If he manages to do this without being spotted, the corpse may provide the final pollutant push that sends the rest of the fish into a sudden crisis. Unless your tank is well understocked, it is vital to reassess stocking levels at regular intervals. Fish such as plecs generate a lot of waste for their body mass. They are usually sold as tiny specimens, and when you see it every day you might not be aware that the three inches of fish you budgeted for is now a foot long waste generator. You should have considered the adult size of the fish when you bought it, but if you didn't you aren't alone. At least half of the baby plecs sold are to people who do not realise that the fish is nowhere near suitable for your average three foot community. This is why the more responsible fish shops have tanks full of giant plecs, returned to the store by unwary purchasers. The more responsible fish shops do actually take them back. The less responsible ones just tell you that you shouldn't have bought it. Many years ago I took a 'behind the scenes' tour of London Aquarium. What's behind the scenes, among other things, are three huge vats, which are home to a collection of abandoned giants. Plecs, Oscars, and the bigger gouramies appear to be particular pitfalls for the general fish-buying community. Of course there's just no excuse for someone who buys a red-tailed catfish!

Live-bearer fans also regularly have overstocking problems. The fish don't grow much, but an unmonitored tank with an adult female guppy in it will have hundreds of guppies in it within a very short space of time. Not having a male will not fix the problem - most guppies are already pregnant when they come home from the shop. Although in an average community most unplanned fry will be eaten, there will be a few survivors from each brood, and you might be a bit startled when you do a head count.

If you have opted for a planted tank, you will find that plants do not stay the same. If they are healthy, they grow. If they are not healthy, they die. Either can cause problems in your tank if not monitored. Excessive plant growth can actually choke the fish, filling all the available space until there is nowhere for them to swim. Although everyone knows that plants photosynthesize, taking in light and carbon dioxide and producing oxygen, many do not consider that plants also respire - using oxygen and producing carbon dioxide. In the light the oxygen produced by photosynthesis far exceeds the amount used by the plant, but, when the lights go out photosynthesis stops, and then the plants are purely consumers. A massive excess of plants can cause oxygen shortages when not photosynthesizing. Alternatively, if your plants go the other way and die, each leaf that is rotting in the tank is producing poisons as it breaks down, just as a dead fish rotting would do. If there is a lot of rotting vegetable matter, this will be an excessive strain on the filter. You need to watch your plants in the same way you do the fish, removing dead ones, and, if they thrive and flourish, removing excessive live ones!

In the complex ecosystem of the aquarium, conditions are always shifting and adjusting, usually in small ways. However, if a particular balance shifts too far then the ecosystem may not be able to adjust, and a crisis will follow. If you always keep an eye on your tank to determine if the conditions are changing, you will be able to fix the problem before it starts, by small changes. Big changes are the enemy of the fishkeeper - by a regime of tiny adjustments as required you will keep your little ecosystem on an even and uneventful keel.

This article has been kindly provided by Kathy Jinkings and cannot be reproduced without her permission

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