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  • Aquarium Conditions

    Aquarium Conditions

    Author: Warren Stilwell
    First published in Aquarium World November 2000

    This article is based from experience and many of the insights contained in the book ‘The Optimum Aquarium’ by Kaspar Horst/Horst E. Kipper (ISBN3-925916-02-4). This book is a wealth of knowledge for anyone who strives for perfection. Unfortunately this article assumes a certain basic knowledge about water chemistry that might go beyond what some people are willing to research, but do read on anyway, it’s not all like that.

    One of the most pleasing looking aquariums is that which mimics nature as closely as possible. This can be quite challenging given the limited space and budgets imposed upon us. If we are to expect the best from our hobby and the best for our pets we must aim towards creating this goal. It is however not always practical to try to imitate nature exactly, as in many cases it would be highly unstable. Below details two ways of setting up an aquarium system that will cater for almost all types of fishes.

    There have been major advances in technology for aquarists over the past few years. Most of these advances are not mentioned in the many books that are available today to help us with our hobby, passion, or obsession. This is due to most of the literature being at least 10 years old, and written by people who have successfully kept fish for many years without this technology.

    Many of us have less than optimal conditions in our aquariums. This comes about for many reasons. Some of us are too busy. Others do not want the hassle of regular testing and lots of maintenance. In today’s society it seems there is always less and less time available for our hobbies. There is hope however. Much of the new technology available today helps reduce maintenance, and can extend the time between water changes. Alternatively, it can improve water quality in an existing system. These, of course, do come as a financial trade-off, but what doesn’t anymore? All this said however, there is no substitute for regular care of our pets.

    The Goal:

    We all want a clean looking aquarium with no or little algae, lots of colourful fish, and no need for water changes. Well, unfortunately this cannot be achieved easily, and water changes will always be required. In nature the ratio of water to fish is millions times what we have in our aquariums. Even if there are 100 fish in a 1m2 area, this is compensated for by 1000 litres per second water change or 100,000 litres of water around them where there are no other fish. These 100 fish in our aquarium must however cope with only 250 litres of water which is recirculated (not changed) maybe 2-5 times per hour. Waste products and unwanted nutrients build up very quickly in a small closed system like this. Typically in smaller tanks the problem is worse, while in larger tanks it is better.

    Water Chemistry:

    In nature the water is relatively low in algae producing nutrients. In many areas the water is very soft (1dH or less) with the exception of Africans and a few other specific species. If these conditions were replicated in the aquarium, many things would start to go wrong immediately. Because there are virtually no nutrients in very soft water the PH can change very quickly as the fish waste product builds up. In nature there is stability only because of the massive amount of water volume or water flow.


    Set up a 100 litre tank and fill with distilled water. Add sodium bicarbonate (Baking Soda) to get a carbonate hardness of 1dH. Add sulphuric acid to adjust the pH to 7.0. 100 litres is quite a lot of water, but you would be surprised to find that is only takes ½ a teaspoon of baking soda to get 1dH carbonate hardness. It also only takes a few drops of acid to bring the pH down to 7.0.
    If this tank is left covered and sealed in the sun for several weeks, virtually no algae form, and the pH will remain relatively stable. If this tank is then uncovered, gases will dissolve into the water and change the pH. Only a small amount of gas can dissolve however, so the resulting change in pH can be compensated for with either acid, if pH goes up, or baking soda, if pH goes down. After many weeks, a small amount of algae may start to form in the tank. This is due to dirt and dust falling into the now uncovered water. This dissolves and starts to build up a nutrient load. Algae spores also float in the air and land in the tank. Now that there are suitable nutrients and algae spores, algae will start to grow. The quantity of algae however is very small.

    We now introduce one very small fish, a neon for argument sake. This neon must be fed, which will leave uneaten food to pollute the water. The neon also releases waste products into the water. After 1 day of feeding and waste production from the one tiny fish, there are more nutrients in the water than in weeks of having no fish and the aquarium. Within days algae start to form in significant numbers, and by the end of 2 weeks the glass is covered with thick algae, and the water is green. Also massive pH shifts have occurred that, left unchecked, will kill the fish. All this has happened with only the faintest trace of pollutants in the water. This highlights the problem of keeping fish in a closed system, and indicates the need for some way to clean the water.

    Setup Types:

    There are only 3 ways to set up an aquarium so that it is low maintenance and relatively algae free. The first is the easiest, and long term is the cheapest. This is the heavily planted tank with a small fish load. The second is for aquariums that cannot be a plant tank – large cichlids, plant eaters, or African cichlids. The third is to condition the water coming into a tank to the correct pH, hardness and temperature before it enters the tank, and have a continuous water change system that changes the water 1-5 times a day. The third method is often not practical and being self explanatory will not be detailed.
    Many of the requirements mentioned below are required for both types of aquarium, but type 2 is mentioned first.

    Setup type 2: Large Cichlids, Plant Eaters, and Africans.

    Large cichlids continuously disturb the substrate, digging nests, or just digging for fun. Plant eaters are often so voracious that no matter how many plants, and how few fish you have, the plants always lose. Also, this type of fish often seems to delight in biting the plant off near the roots so you find the top 90% floating at the surface. The plant is often then useless, as it will not re-root before dying. African cichlids require water conditions that do not suit plant growth as the water is too hard. There are some plants which will survive but will not grow fast, or well enough, to out-compete the algae. There are of course exceptions to these rules where someone has got lucky with their setup, but that is what it is, luck. This type of setup is often not repeatable on a large scale without significant problems occurring.

    The only way to be successfully algae free in a plant free tank is by fine mechanical filtration, massive biological filtration, chemical filtration and regular water changes. The water changes must be quite large (at least 50%), and done often (once a week minimum). Massive water flow through the filtration is required also, at least 5 times the tank turnover per hour. The filter must also be large.

    Basic Setup:

    It is possible to use an undergravel filter and coarse gravel (4-10mm) for this setup. The only problem which may occur with some species is that they might dig right down to the undergravel plates, rendering this filter almost useless. An external power (trickle is best) is required to get good water conditions. It is only necessary to create a natural looking habitat for the species you wish to keep.

    Mechanical Filtration:

    The best success can be achieved using a pleated cartridge filter of 10 to 15 microns. The most common type is used on Spa Pools to remove debris from the water. The purpose of this filter is to remove all small non-dissolved organic matter from the water. This filter is changed every few days. This stops the organic matter from decomposing in the tank or filter system and increasing the nutrient load.

    Biological Filtration:

    A large surface area of biological filter is required. This is best in the form of a trickle filter. There are many different types of media available for biological filtration, but the best is usually synthetic media with extremely large surface area (450m2 to 1350m2 per litre of media). This will ensure that all dissolved nitrogen compounds are quickly turned into nitrates. As long as nitrates are low (less than 20ppm) algae will be minimal. In some of the newer synthetic media, anaerobic areas will form that will also help to lower the nitrate level. Water changes are still required, however, to keep nitrates under control. There will be more to come in a special article about filters in the next Aquarium World.

    Chemical filtration:

    This is paramount to stop algae forming, and keeping the water clear, sparkling, and to keep unwanted nutrients to a level below the alga threshold. Carbon is good for removed the aged yellow look of the aquarium water, but does little else to stop algae. It does not remove significant phosphate from the water. All organisms require phosphate to survive. It is one of the major building blocks of life. The problem is that you add phosphate to the aquarium regularly in the food. Phosphate absorbing resins are the best solution to lowering the level to that required.

    Water changes:

    Water changes are 100% essential. The time between water changes is much too long in many cases. The regularity will largely depend on the size of the filter, number of fish and the size of the tank. It may be possible to skip changing the water in an aquarium for 3 months, but just think how you would feel wearing the same clothes for the same time. Most of the successful breeders in the world do daily or even twice daily water changes of up to 90%. Your fish will appreciate the maximum amount of water change you can possibly do. This does not mean changing 90% every day, but it is amazing what 10% a day can produce.
    However, many tap water supplies around the country are rich in phosphate, and many brands of activated carbon release a small level of phosphate into the water when first installed in the filter. A 100% phosphate free water source must be used for water changes otherwise the algae are just being fueled. A target level for phosphate in aquarium is below 0.1ppm. If you have a 1000 litre barrel of distilled water, this equates to 0.1 grams of phosphate (about enough calcium phosphate powder to cover your small fingernail). This is a very small amount. Of course, if you are breeding fish in an all glass tank, and can regularly wipe the algae off the glass this is not a problem. It is often not practical to try to remove the phosphate from the water if the amount required is large.

    Setup Type 1: Planted Aquariums.

    The planted tank can house a very wide variety of the commonly kept and possibly more popular smaller fish. Many of these fish prefer heavily planted tanks as it is closer to their natural habitat. The setup of a planted Aquarium is very similar to the previously mentioned system. There are some major differences however. The plants in a heavily planted aquarium work as a filter. They use nitrogen waste product from the fish and uneaten food. If the correct ratio of fish to plant is used it is possible to omit certain filter items.

    Planted tanks require quite soft water, and a pH of 6.5 – 7.0. A good compromise is 6.8. This suits most of the fish that would be kept in this type of aquarium, and is also best for the plants. The most important part of this type of aquarium is the plants, the fish are secondary.

    Basic Setup:

    Undergravel filters cannot be used for this setup. Gravel of 2-4mm is best as a substrate. Iron containing additives can be added to the lower layer of the substrate, but it is not essential if regular substrate fertiliser is used. Undergravel heating is also very beneficial. When planting out the aquarium, at least 80% of the aquarium must be covered initially, and no fish added until the plants have settled in (4-6 weeks).

    Mechanical Filtration:

    The same mechanical filtration is required, however it can be quite a lot smaller. This is due to a lower waste product load on the system. Much of the collected organic matter will be from dead plants, where it would be uneaten food, and fish waste in the other system. The same requirement for changing the filter exists (4-7 days). The more often this filter is cleaned / changed, the cleaner the aquarium is, and less bio-load there is on other parts of the filter.

    Biological Filtration:

    This is also the same. There will be less nitrogen compounds for the filter to process due to the plants however. The filter is a safety mechanism an also helps to provide water circulation.

    Chemical filtration:

    This is often not required any more, or maybe occasionally to just take a slight yellowing off the water. The plants are so effective at cleaning up that this type of filtration is seldom needed. If all is set up correctly and relatively balanced, the plants will utilise all the available free phosphate.


    Planted aquariums need regular fertilisers. The type of fertiliser will depend on the conditions, fish load, lighting, CO2 and water changes. The nutrients contained in the fertiliser are extremely important as they must benefit the plants, but not promote algae. A good water fertiliser should not contain any phosphate and be rich in iron. A good substrate fertiliser should be rich in iron, and contain some nitrogen and phosphate. In both there should be trace elements in the correct quantities. The objective is to sustain a balance of the correct nutrients, with no one nutrient becoming dominant. This is achieved by regular water changes and the daily addition of fertiliser. The contents of the fertiliser are unfortunately beyond the scope of this article as it would be equally as long is this one.

    Water changes:

    Water changes are still required. In this type of system, it is more vital that water changes are done. The previous system will forgive to a greater or lesser degree a missed water change. A planted aquarium will quickly begin to show you when you need to do a change. It is of course better to do a change well before this, as it takes a while to recover from such an event. Regular water changes keep a more constant balance. Other than water, the less you change (pH, hardness (dH and kH), nutrient levels etc) the better of all your aquarium inhabitants will be.

    Water Chemistry 2:

    As previously mentioned, it is not practical to try to keep natural conditions in an aquarium. Only when a carbonate hardness of 4dH or greater is sustained will the pH be stable. In an African tank the dH will be much higher anyway. The target is to research the required water chemistry for the species you wish to keep and as best as possible create it with the above exceptions.

    Happy Fish:

    If the natural conditions for the species are created, they will be more active, spawn more readily, and grow faster and stronger. To achieve best results a limited number of complementary species should be grouped together, with the ultimate system containing only one species. On the whole, if breeding a specific fish is the target then a single species tank is essential (sometimes 1 or 2 fish of another specific species will be required to initiate spawning). Fish that compliment each other are those that are found I nature living together. It is not practical or wise to put a Neon and an African together for example. Apart from the Neon requiring soft low pH water and the African requiring Hard high pH water, the African will probably also eat the Neon. In many cases incompatible fish are mixed together and while they might survive, they are not at their best.


    Setup Type 1 costs a little more to get going because of the large outlay for plants. The long term running costs are much lower however, – fertiliser (that you can make yourself) and mechanical filter cleaning products are the only on going costs.
    Setup Type 2 is a little less expensive to get going, but has relatively high running costs. The quantities of activated carbon and phosphate resins are quite large. They are also not cheap. The same cost for mechanical filter cleaning product exist.

    Ways to get Good Water:

    Good water, – what is it. As previously mentioned, good water has no phosphate, no nitrate, nitrite, or ammonia, and has the correct PH and hardness for the species of fish(es) you keep. To obtain this there are several methods.
    If your tap water is suitable, use it you are very lucky. It pays however to monitor the quality of your water as it can change from winter to summer as the demand for water changes. Water fed from wells often changes quality depending on the quantity of water drawn from it and what it passes through on the way to your tap.

    If your water is unsuitable there are several alternatives:
    Rain water. This is often quite good, but can be too soft for Africans and many harder water species. Care needs to be taken here because pollutants like heavy metals and hydrocarbons can sometimes appear in the rainwater. These are toxic to your fish.
    Processed tap water. If you can store water in a separate tank and process it with phosphate and ammonia removing resins it is possible to get suitable water. This can also be pre heated to make water changes easier.

    Reverse Osmosis. RO water is by far the best, but is far too pure to use on its own. It also needs to be stored separately from the tank so it can be conditioned before being used. Salts and trace elements must be added before RO water is suitable. This stabilises the pH also. It too can be preheated.

    De-Ionised water is as good as RO water, but is often very expensive to produce. It requires the same conditioning as RO water.

    The above methods (especially RO) may need extra salts and trace elements added to the water before it is suitable for the species of fish it is intended for. The requirements for these salt and trace elements are also beyond the scope of this article, but will be detailed in an article in the next Aquarium World.


    The overall aim is to make our fish as happy as possible. This is a challenge that gives us pride in our hobby once we achieve it. There is nothing better than sitting down in front of a good display aquarium to enjoy its beauty and see the occupants behaving as if or almost as if they were in the wild. This is more so when it is your own aquarium.
    Most of the information you need to set up the correct conditions is in books, and quite often on the internet.

    Good Books:

    The Optimum Aquarium (Kaspar Horst / Horst E Kipper) ISBN 3-925916-02-4
    This is an excellent reference book that covers planted aquaria.

    The Biotope Aquarium (Rainer Stawikowski) ISBN 0-86622-519-6
    This is an excellent all round book that details the basic habitats of nearly all type of fish.

    The Natural Aquarium (Satoshi Yoshino and Doshin Kobayashi) ISBN 0-86622-629-X
    A different book but similar to the Biotope Aquarium.

    Nature Aquarium World 1,2 and 3 (Takashi Amano) ISBN 0-7938-0089-7

    There are three books in this series. There is limited information in them, but it is all good. The emphasis is totally toward the planted aquarium. The photographs are nothing short of incredible. The series gives you examples of many different themes for a planted tank, and once read you will not be able to settle for just one aquarium, you will have to have lots.

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