Shane's World Right Arrow CatfishologyRight Arrow Fishkeeping Basics

Article © Rupert Collins, uploaded October 08, 2007.

A huge variety of aquarists (aquarium owners) of every age and level of experience use this web site frequently, but certain issues crop up again and again in discussion. In this article I aim to address some of the more basic pitfalls, and to help people work out where they could be going wrong.

Planning your Aquarium
This is by far the most important stage in setting up a successful aquarium. Knowing exactly what you want from the tank and how you want to achieve it is enormously important. This cannot be emphasised enough. These are the sort of questions you will need to ask yourself:

  • Is there a specific fish you want design the tank around?
  • Do you want to keep plants?
  • Are you trying to recreate a habitat?
  • Do you want the tank to be integral to the design and style of your home?
  • Are there any obvious constraints (e.g. high temperatures)

By being clear and focused from the beginning you can tailor the equipment you buy to suit your needs. Always buy the biggest tank you have room for, or can afford. Larger tanks have many benefits. They provide a more stable environment for the fish, as any fluctuations in water quality (pH/temperature/nitrates etc) will be more gradual. This allows you more time to identify and deal with problems. You will also have more choice in which fish you can include.

Apistogramma bitaeniataApistogramma bitaeniata

The quality and type of your water supply is crucial in deciding which fish you are able to keep. The most important factors are hardness, pH and nitrate levels (more on these later). Choose fish that are happy in the type of water you are able to provide for them. Most fish are quite adaptable, but for example; wild cardinal tetras, discus and dwarf cichlids (Apistogramma spp.) do not often thrive in hard alkaline tap water. The golden rule here is to do your homework. By reading books and using internet forums you can make a list of fish you like, that are also happy in your water.

Many people neglect the temperature of their aquarium. Many common species are quite adaptable, but do be aware of their needs. For example, species such as danios and many Corydoras like cooler water (20-24°C / 68-75°F), while fish such as angelfish, discus and some fancy plecos like warmer water (26-30°C / 79-86°F). Keeping fish in water that is too warm may deprive them of oxygen and reduce their life span . Keeping fish in water too cold for them can increase their susceptibility to diseases.

Your water company will almost certainly add chlorine to your water to disinfect it. Chlorine damages the gills and skin of fish, and can kill them. It should always be neutralised with a tap water conditioner. As chlorine is a gas, it can also be removed by aerating the water with an airstone for 24 hours. Many water companies however are now switching their water disinfectant to the more stable chemical chloramine, which cannot be removed by aeration. Chloramine is also toxic to fish, and can only be neutralised with a tap water conditioner available from your LFS. Make sure the tap water conditioner you use can also deal with chloramine. Your water company can tell you which method they use in your area, but may switch without informing their customers.

Filtration and the Nitrogen Cycle
Filters are the life support system for your fish. They remove the visible detritus (muck) from the tank as well as invisible pollutants. Biological filters work by providing a home for colonies of bacteria. These beneficial bacteria consume and break down harmful fish waste into less toxic forms. The waste fish produce is very rich in what are called nitrogenous (nitrogen based) compounds. These are found in the aquarium in three different forms: ammonia, nitrite and nitrate. They are all undesirable in the aquarium, but in varying degrees. See below.

Produced directly as waste from fish, dead plants and uneaten food etc.
Very toxic to fish, even in minute quantities.
More toxic in alkaline water.

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Less toxic than ammonia, but still harmful.
Stops fish from breathing by blocking oxygen uptake into the blood.

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Much less harmful than the above, but can affect the immune system,
cause stunted growth and poor breeding success when levels get too high.

When a tank is first set up, none of the necessary bacteria are present and any fish are at considerable risk of being poisoned by their own waste. This is why a tank needs to be matured gradually. This is often referred to as "cycling". It can take up to three months before a tank is is fully cycled. An essential purchase for the aquarist is a set of good quality test kits. Test kits for the following are essential: ammonia, nitrite, nitrate and pH. Test kits, although expensive, take the guesswork out of fishkeeping. When setting up a new tank they tell you exactly when its safe to add fish.

Fish produce waste in the form of ammonia, which is consumed by filter bacteria to form nitrites, which is in turn consumed by a different set of bacteria to produce nitrates. These bacteria grow on all surfaces in the aquarium, but are found in greatest numbers in the filter. A large surface area is provided by the filter media (which is usually a mixture of foam and porous materials) with a constant supply of food from the fish's waste as well as oxygen. In order to mature your filter you will need to provide a source of ammonia for the bacteria to feed upon. This used to be done by adding a few hardy fish such as guppies, which could withstand the high ammonia and nitrite levels of the first few weeks.

Nowadays we don't need to subject our fish to this kind of pollution as new techniques have been developed. By adding an ammonia source in the form of some fish food (an algae wafer or two on a saucer is ideal), and measuring every day with the test kits, you can be certain that your biological filter is matured before your fish arrive. There should be an initial peak of ammonia, followed by a peak of nitrite which is followed by a peak of nitrate. Maintain an ammonia concentration of about 2-3ppm (mg/l) by adding more food when necessary. When your ammonia/nitrite levels fall, and nitrate levels build up (usually after about 6 weeks), perform a 25 % water change and add your first few fish. Only add a few fish at a time, feed sparingly, and monitor ammonia/nitrite/nitrate levels every day. If any ammonia or nitrite is detected, perform a 25% water change. If all goes well, keep adding a few fish every week.

The cycling process can be helped along considerably with the addition of some filter muck or gravel from an established tank. This will kick-start the process by providing the bacteria. Be careful not to add any from tanks that have recently had a disease problem. Bottles of bacterial culture are available from the LFS, but these are often limited in their effectiveness and are no substitute for the real thing.

When the tank is fully mature, any ammonia the fish produce will immediately be consumed by the bacteria. The amount of bacteria in the tank is at a level in keeping with the number of fish you have. Adding lots of new fish at once will mean that the bacteria will not be able to multiply in time and a harmful increase in ammonia may result. If a filter is too small, it will not be able to provide enough space to house all the bacteria that is needed to support all the fish. As a result, a common problem is aquarists not providing enough filtration for the fish stock.

When choosing a filter, again, bigger is better. A larger filter will help compensate for any mistakes that may happen (such as some uneaten food or an unnoticed dead fish). Although some fish don't like a powerful current, you can still use an oversized filter by removing the spray bar or by deflecting the current on the aquarium sides. By far the best filters for the average tropical aquarium are the external "power" filters. These filters have a large volume of media, are more adaptable, and use less tank space than the internal power filters. These internal power filters, although commonly used, block easily and often have a very small amount of filter media. Along with the air-powered box/sponge filters, the internal power filters are however a good choice for a lightly stocked or breeding tank. Undergravel filter plates combined with powerheads are not very popular nowadays but are still effective. A thick gravel bed (7-10cm) provides the medium for the bacterial colonisation. However, rooted plants do not often flourish with them and they will not work if there are dead-spots caused by large rocks or bogwood.

Decorating your Aquarium
The main purposes of the tank decor are to make the tank look visually appealing to the owner and to provide the correct environment for the fish. A lot of aquaria are not imaginative in their design, which can lead to their eventual neglect. The best place to begin is by returning to why you want the tank. If the tank is for a specific fish, then why not design the tank around that fish and its requirements. If the tank is to be part of the decor of your home, then make sure any fish you keep will be happy in that environment.

Many people talk about biotope aquaria where all the fish, plants and decor come from a specified geographical habitat. This in reality is often very difficult to achieve as the goal is often too vague. For example creating a true "Orinoco" biotope in a tank would be impossible, as this river is many thousands of miles in length and varies in character considerably (even in one location). Another problem with biotope tanks is the lack of available fish species and habitat data from specific areas. Rather than a biotope, it is often more convenient to create a theme tank. With a theme tank you can be more flexible with mixing species from different areas provided they like the same hardness, pH, temperature and current. Themes such as a mountain stream bed, a driftwood snag or a plant rich swamp are popular, but you are only limited by your imagination. Visit a local river or lake for inspiration.

A natural catfish aquarium. Photo: Marc Stabel
A natural catfish aquarium

The tank bottom is known as the substrate. Be sure that you make the right decision from the outset, as changing the substrate can be tricky when the tank is stocked. Most people choose 4-8 mm pea gravel, but there are many other options. I will discuss the requirements of live plants later, but if substrate rooted live plants are not desired then only a bare minimum of substrate is needed to cover the bottom of the tank. Any more than one or two centimetres will make cleaning more difficult and harbour excessive bacteria. Loss of barbels (whiskers) in Corydoras is often the result of a stagnant substrate.

Sand is often a substrate which is avoided by beginners, but is really quite easy provided a few rules are adhered to. As with gravel always use less than 2cm. The rooting action of many fish (especially catfish) will prevent compaction and stagnation, but you can run your fingers through the sand every week to help the process. Always position your filter inlet at least three inches above the sand to prevent it being sucked into the unit. A really natural look is to blend different substrates together such as sand, gravels and pebbles.

Some types of sand have the potential to alter the water chemistry of the aquarium. Calcium carbonates in products such as coral sand will make the water harder and raise the pH. This is not desirable unless you plan to keep fish that enjoy those water conditions (such as Malawi cichlids). If in doubt buy sand from a reliable LFS, and only buy "silver", "river" or "play" sand which will not affect the water. Testing a trial water sample with a pH test kit is also a good plan. Always wash the sand thoroughly prior to use.

Bogwood (or driftwood) is a firm favourite with fishkeepers. The most hassle free way to source bogwood is to buy it from your LFS although it can be expensive. Before adding bogwood to your tank, it is a good idea to first boil it to kill any fungus. Large pieces can be put in a dishwasher (without detergent). It is also good to soak the wood for at least two weeks to get the worst of the tannins (brown staining) out. Even after soaking for two weeks the wood will still stain the tank water to some degree. The tannins are natural and will not harm the fish, but they can be removed by adding carbon to the filter.

Rocks and stones are very useful in aquascaping, and the same advice applies with regard to altering water chemistry. Inert rocks such as slate and granite will not affect the water. When keeping catfish always avoid rocks or gravel with sharp edges, as this may damage their sensitive barbels.

A stunning planted tankA stunning planted tank. Photo: Whitepine

The subject of aquarium plants deserves more attention than this article can provide, but I shall try to point out some of the common mistakes people often make. Plants are generally observed to be more difficult to keep than fish, but with a little attention to their needs, you can begin to stack the odds in your favour. The real plant enthusiast can spend a fortune on undergravel heating cables, pressurised CO2 and metal halide lighting. This expensive approach often produces the excellent results you see in books and magazines, but a few tips will help people have more success on a modest budget.

The substrate is commonly overlooked where plants are concerned. Usually the gravel layer is too shallow and the gravel too large in size, which restricts root development. Try either sand or fine grade (2-3mm) gravel/grit at a depth of at least 10cm for good rooting.

Obviously lighting is essential to plants for their photosynthesis. Generally speaking, more lighting is usually better. Just trying two fluorescent tubes instead of one can often make a big difference. Buying tube reflectors is a cheap, effective way to increase your lighting. The new ranges of T5 tubes will also give you more wattage for your money, but always remember to buy tubes specifically designed for plants. Having the lights on for between 10 and 12 hours per day will give best results. Reduce this if algae becomes a problem (more on this later). A mechanical timer is invaluable in giving your plants a stable environment.

Another essential ingredient of photosynthesis is carbon dioxide (CO2). Along with insufficient light, a lack of carbon dioxide is often the limiting factor to plant growth in the aquarium. Water is limited in its capacity to hold carbon dioxide, so many aquarists supplement this with pressurised dosing or yeast fermentation systems. Understandably this high-tech approach is not desired by all aquarists, but a simple adjustment to the filter may help boost carbon dioxide levels enough to make a difference. When the water's surface is disturbed, dissolved carbon dioxide escapes into the air. By removing surface agitation from spray bars and airstones you will reduce the rate that carbon dioxide is removed from the aquarium, thus improving conditions for plants. Do be aware that this technique will reduce the amount of oxygen in the water, and should not be used with fish that require high levels of oxygen (such as many plecos).

As the growth of plants is limited by both CO2 and light, they are both interlinked, so one without the other will not result in more growth, but in more opportunistic algae. Providing vastly upgraded lighting with no extra CO2 is likely to end up with increased algal growth. Achieving the correct balance between the two is essential to a successful planted tank.

Choosing plants is often down to personal aesthetic tastes, but unfortunately what looks good doesn't always grow. Many people unwittingly buy terrestrial or bog plants (such as Dracaena sp.) from aquatic shops, and these always have a short life span underwater. Always purchase true aquatic plants. A good quality book combined with trial and error is usually the best method in finding plants that will thrive in your set-up. Below is a list of species that can do well in the low-tech aquarium:

  • Anubias spp.
  • Cryptocoryne wendtii beckettii
  • Vallis (Vallisneria sp.)
  • Hygrophila polysperma
  • Java fern (Microsorum pteropus)
  • Red Amazon sword (Echinodorus osiris)
  • Hornwort (Ceratophyllum demersum)
Anubius barteri
Anubias barteri var. nana
Cryptocoryne beckettii
Cryptocoryne beckettii
Microsorum pteropus
Java fern (Microsorum pteropus)
Hygrophila polysperma
Hygrophila polysperma

Anubias and java fern are particularly useful, undemanding and attractive plants. They should both be attached to bogwood (with fine wire) rather than being rooted in the gravel, so this removes the need for a thick layer of gravel. They also don't require intense lighting, and are too tough for many fish to nibble on. Remember to treat plants as though they are fish when you purchase them. Always acclimate them slowly to your water conditions, especially if water conditions are different to those in the shop.

Stocking the Aquarium
Choosing and buying your fish is the most exciting part of the hobby for most people, but sadly too many people purchase fish that are not suitable for their set-up. This is often down to impulse purchases, lack of information or most frequently, bad advice from shop staff/displays. Many shop staff are brilliant, but unfortunately many others are ill-informed, so it is often best to get a second opinion before purchasing fish. Internet forums are great places to get information. Forums are moderated and peer reviewed, so bad advice is quickly corrected.

As stated before, always purchase fish that will enjoy or adapt to your tap water. Water hardness (amount of minerals in the water) and pH (how acidic or alkaline the water is) are the two factors to be concerned with. Usually if the shop is local, it will be on a very similar water supply to yours, so the fish will already be acclimated (accustomed) to the same water. Sometimes wild-caught fish are kept on soft water systems in the store, so always ask before you buy. If your water is significantly different from that of the shop's, then a long acclimation period is necessary to allow the fish to adjust. First of all, turn off the lighting and then empty two thirds of the water from the fish bag. Next, float the bag securely in the tank. Then add a dribble of tank water every 10 minutes until the bag is nearly full. Allow 2-3 hours before releasing the fish. If your water is similar to the shop's, allow approximately 30 minutes.

The number of fish you can keep in your aquarium is a much discussed point. There is a common myth in the hobby that fish will only "grow to the size of the tank they live in". This is indeed a myth, but has an element of truth. In an overstocked tank nitrates will often be very high, which may cause reduced growth rates and stunting in the fish. Nitrates will also impair the fish's immune systems and lead to disease, so overstocking is not a good idea. Its best to plan that the fish will grow to the size that it is genetically programmed to. In reality, your stocking level is limited by a number of factors including:

  • Amount of oxygen available
  • Concentration of nitrates
  • Effectiveness of filtration (ammonia/nitrite surges after feeding)
  • Aggression between fish
  • Capacity to cope with equipment failure/power cut
  • Potential of fish to grow

The two inches per gallon stocking rule is a good general guideline, but stocking ultimately depends on the above factors. Choice of fish also makes a big difference, as a 6" oscar will produce much more waste, and therefore take up more stocking space than a 6" twig catfish.

You can increase the amount of oxygen available by using airstones and spray bars to break up the water's surface. Nitrates can be diluted with increased partial water changes. Aim for a maximum nitrate concentration of 50mg/l, but bear in mind that some sensitive or wild-caught fish will not tolerate levels this high. Always try to keep nitrate concentrations as low as possible. The effectiveness and reliability of filtration and heaters can be improved by over-sizing and sharing the load. A tank with two or more filters and heaters will take much longer to reach disaster point if there is an equipment failure.

If in doubt, post a thread in the forum listing your potential stock, tank size and current equipment. If you think you are pushing your luck as far as stocking goes, then you probably are. Aquatic shops will usually be happy to take away surplus stock.

The most common reason that fish die in the aquarium is due to overfeeding. It is much easier to kill fish by overfeeding than underfeeding. Many fish naturally binge feed in the wild as food supply is often seasonal and short lived. In the aquarium if they are fed too much, the food may either remain uneaten or pass through the fish undigested. Dried prepared foods are often rich in protein, and will quickly break down into dangerous quantities of ammonia should the filtration not be able to cope. Its very hard to say how much to feed, but it is generally better to feed little and often. High levels of nitrate indicate overfeeding.

As with humans, a varied diet is best. We can never exactly replicate a fish's diet in the wild, but by varying different foods we are able to hopefully address any shortcomings. By researching your fish thoroughly, you will know which foods are preferred. There are several excellent articles on Planet Catfish with regard to feeding catfish. A combination of frozen foods (larvae), dried prepared foods and vegetables will keep most fish healthy. Observe the fish closely, and ensure all fish (especially nocturnal catfish) get their share.

Avoid those holiday feeding blocks. Healthy fish can survive for weeks without food and are often loathe to accept new foods instantly. If you feel the fish do need feeding on holiday, parcel up smaller than normal portions for a reliable fish-sitter to give every other day.

Tank Maintenance
In order for your tank to thrive it needs constant maintenance and attention. Regular partial water changes are essential to keep the fish happy. The greater your stocking level, the more frequent and large the water changes will need to be. Water changes are necessary to dilute the pollutants that build up in the tank over time, and replenish the buffers that keep the pH stable.

A good rule of thumb though is to change about 25% of the water each week. Try to siphon as much detritus (muck) from the gravel as possible as a build up of this can cause the pH of the water to destabilise. Clean the filter media when the filter output starts to drop, but always use old tank water as the chlorine in tap water will kill the filter bacteria.

Algae is often the bane of many aquarists' lives. You cannot remove algae from the aquarium completely and you would not want to, as a small amount is beneficial to the functioning of the tank. It is when algae starts coating glass, decor and plants that it becomes a problem.

By far the worst course of action is to add a algaecide from a bottle. This does not address the root cause and can create oxygen problems when the algae dies. Another common mistake is to add algae eating fish such as bristlenose plecos or Otocinclus. Again this does not address the root cause of the algae and the addition of more fish in some cases may make the problem worse. These algae eating fish are often very choosy in the type of algae they eat and will only usually consume the soft brown and soft green types. If these types are removed they could be replaced with algae that will not be eaten.

Oedogonium sp.
Green fuzz algae (Oedogonium sp.)
Cyanobacterial algae
Cyanobacterial "algae"

Algal blooms are usually caused by excessive nutrient and/or light levels. Nitrates and phosphates are powerful fertilisers, and if they are not kept in check with frequent water changes, algal blooms are often the result. If your tap water is rich in nitrates and phosphates you may wish to consider a water purification method such as reverse osmosis (RO) or resins.

Reducing the numbers of hours of light the tank receives will also help, as will preventing sunlight reaching the tank. Changing the fluorescent tube can make difference as they will deteriorate after about a year, and produce a spectrum that favours algae. Another tip is to add some fresh bogwood to the aquarium. The brown stain from the tannins will dramatically cut down the available light to the algae, and combined with increased water changes will often be enough to knock the algae back. Encouraging growth of plants will help them to out-compete the algae for nutrients and light.

The subject of disease deserves an article to itself, but here I will explain some of the basic do's and don'ts. even the best aquarist's fish suffer from diseases at some point, but if dealt with correctly it need not always be a disaster.

The best way to prevent disease is to always quarantine new fish in a separate aquarium for at least 3 weeks. You can observe and treat diseases much more easily, and allow the fish to acclimate to your water in peace. Unfortunately not every aquarist is able to devote a spare tank to quarantine and immediate release into the main tank is usually the only option.

Although most aquatic shops try their utmost to reduce diseases, it is inevitable that with high stocking levels, rapid stock turnaround and stressed-out fish, some diseases do crop up from time to time. Observe your fish closely during the first few weeks after purchase, as this is when most disease outbreaks occur.

If you suspect your fish are not acting normally, not eating, or have any change in appearance, the first stage is to diagnose the problem or potential disease. Too many people suspect a disease and rush down to the LFS to buy a bottle of medication. It can't be emphasised enough that chemical remedies should only be used when you know without doubt which disease you are treating. With the shotgun approach to medication you can easily cause more harm than good, as some treatments can be quite harsh on fish, may damage the filter bacteria and may not address the problem fully. In many instances just changing the water more frequently, cleaning the tank and providing a more suitable diet is enough for the fish's immune system to do the rest. Never mix different medications as the outcome is likely to have unpredictable effects on the fish.

The forum is a great place to get information and diagnosis, but always post clear pictures and provide a detailed description of the symptoms. Once a diagnosis has been decided, an effective treatment can be agreed upon. If the disease is not contagious, it is better to treat in an isolated hospital tank.

The most common disease encountered by aquarists is whitespot (or ich). This disease is a parasitic protozoan which appears as sugar-like white spots on the fish's skin and fins. The parasite is present in background levels in most shops and home aquaria. It is only when fish are stressed and weak that the disease is able to overcome the immune system. If caught early enough the disease can be beaten simply by gradually increasing the temperature over three days to 30°C (86°F) or above. This temperature rapidly speeds up the life-cycle of the parasite and approaches it's natural lethal level. Maintain this temperature for two weeks. Bear in mind that there will be significantly less dissolved oxygen at high temperatures, so provide increased aeration in the form of extra airstones and spray bars. Do not attempt this high temperature technique if this temperature is beyond the tolerance of your fish.

As always, prevention is better than cure. There is no substitute for a good diet and clean water in keeping your fish in top health. If you do get a disease outbreak always ask yourself why; test your water, and try to address the underlying cause.

I hope this article has been of some help. Thanks to all that contributed photographs and good luck with your fishkeeping.

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