Water

Introduction

It is often said that fish keeping is more about keeping water than keeping fish. Certainly if you keep your fish in water that is correctly maintained for them, they will live long and healthy lives. The purpose of this section is to teach you sufficient water chemistry and biology to help you maintain your water in an optimum condition.

If you have a reasonable understanding of science then most of this will be easy. If you feel the whole concept of science is beyond you, fear not – and proceed anyway. While there will be some aspects and concepts that you will be totally unfamiliar with I hope they have been explained in such a way that you can easily follow. If you do get stuck, there is a contact me button at the bottom of every page – it is there to help you, don't be afraid to click it and send me and e-mail. I will try to answer any of your questions.

(For those of you for whom Quantum Mechanics is a breeze who think I'm being a bit simplistic, yes I know, but this is meant to be easy to understand.)

Throughout the body of the text you will find terms which are not explained. These are always clickable links which will take you to a page that gives fuller information about the subject. Please take time to click these links where you don't understand the term (and even if you think you do).

So let's start with the basic water. Everyone knows that water is H₂O, but what runs in our rivers, comes out of the sky as rain or snow, or comes out of the tap is not pure H₂O. It contains a number of other chemicals, as far as fish are concerned there are some good, some bad and some neither. To make this more complicated it depends on the species of fish, and the natural water it comes from, as to what is good and bad.

Acidity and Alkalinity

Water normally contains chemicals that make it either acid or alkaline. This is measured as pH.

When you buy a new fish you should first check what pH it likes. Your local fish store should be able to tell you this (if they can't find a new store) or by reading up about the fish in advance. For this you can either buy a good book on the subject or check on the internet. For this it is a good idea to get to know the scientific name of your fish.

Most fish can live in a fairly wide pH range, and those commonly kept which came from very acid or alkaline conditions have often become acclimatised to the harder water commonly found in our taps. The Neon Tetra Parachierodon innesi originally came from very acid water, but it has been bread in captivity for so long now it is happy in most tap waters

Hardness

Water Hardness was originally a measure of how hard it was to lather soap in that water. This is actually a measure of how much dissolved Calcium and Magnesium there is in the water. It is used in fish keeping to evaluate the total dissolved minerals in the water. The hardness is divided into two types Temporary and Permanent. Temporary Hardness is caused by Bicarbonates and can be removed by boiling the water. It is important in aquaria because it can act as a buffer. Permanent hardness is caused by Sulphates and Chlorides and is inert and not removed by boiling.

Water varies tremendously in its dissolved minerals. Where the water has washed down through limestone (which is Calcium Carbonate) it is very hard, where it is fresh rainwater is is very soft. In tropical Rain Forests the natural organic acids present in the water remove the hardness, so the water in the rivers is very soft and acid - these waters are known as dystrophic.

The Nitrogen Cycle

Fish do not produce urine in the way that mammals do. Instead the excrete Ammonia, either through the kidneys, or directly trough the gills. Ammonia is Toxic to fish, and we need to eliminate it in the aquarium. This is done by a bacteria using a process called Nitrification. Most Nitrification occurs in the filter, be it an under gravel filter, a sponge filter or an external canister filter. The bacteria responsible for this grow very slowly. When you first set up a tank there are not enough of them, and you can get a build up of toxins – this is known as new tank syndrome. Preventing New Tank syndrome requires that you go through a process with new tanks known a cycling.

Nitrification converts the harmful nitrogen compounds to Nitrate. Nitrate is much less harmful, but if it is allowed to build up it can harm your fish. Nitrogen is removed from the tank by Denitrification, and also being absorbed by plants. You can help this process in a number of ways

• Plants absorb Nitrates from the water. The more actively the plants are growing the better they remove nitrates. Plant growth is generally limited by dissolved Carbon Dioxide (CO₂). This can be overcome by adding CO₂ to the tank or by growing floating plants. Indian Fern is particularly good at this.
• Use suitable filter media. These can be inert systems that simply encourage denitrifying bacteria or active systems that chemically remove nitrates,
• Use a Green Filter. This is an external trickle filter with a plant growing in it. Suitable plants for growing in a Green Filter are Swiss Cheese Plant (Monstera) and Philodendron
• A Denitrifying Filter. You can buy these or build your own.

Nitrogen Compound are also increasingly found in tap water. They get there from agricultural run off, where too much fertiliser is added, and from animal waste run off. Where these are very high they can be removed from the water added to the tank by using a chemical tap water filters or reverse osmosis.

Water Changes

Water changes are important in the aquarium for two reasons

• To remove the Nitrates that build up with time
• To replenish other chemicals that are used up, typically bicarbonates which act as buffering in the water

Why should this be - well firstly early aquarists did not understand the nitrification that goes on in the aquarium - indeed Innes does not even mention it. He also says that filters should be washed every week or two and the media replaced, a sure way of destroying the any nitrification that may be occurring. Secondly early aquarists didn't worry too much about chlorine Innes says you only need to worry if it is strong enough to smell or taste. So early aquarists found that when they did a water change the fish tended to suffer, as levels of chlorine which will not harm fish will kill the nitrifying bacteria.

Generally you should change the water in your tanks every two weeks, I change around 25% in a well stocked tank. When changing water make sure you add a good de-chlorinator. Some people say you should warm the water before adding it. I add mine straight from a hose pipe connected to the cold tap and add the de-chlorinator direct to the tank. When doing a water change you should also rinse any filter sponges in old aquarium water to ensure they do not clog.

Cycling the Aquarium

When you set up a new aquarium it does not contain any of the bacteria needed to establish the Nitrogen Cycle. Tap water does not contain any of the appropriate bacteria as they are killed by the water treatment. You must establish the Nitrogen Cycle bacteria in the tank. This process is known as "Cycling".

The bacteria are extremely slow growing, so it takes a while for the numbers to become established. Some people add bacteria cultures - available from good aquatic stores - to speed up the process. I never bother, because I have a number of tanks I just seed each tank from an established tank. This is done by adding gravel or decor from another tank, or by washing the filter sponge from an established tank in the new tank. This must be done after any chlorine in the fresh tap water has been removed.

There are two styles of cycling, either with or without fish. Both styles have their champions. I prefer using fish, but then I am working on a pre-seeded aquarium. Champions of fishless cycling say it kills fewer fish (I can't remember when I last lost a fish cycling a tank).

Fishless cycling involves adding Ammonia or Urea to the tank before you add the fish. Ammonia can be bought from pharmacies and some hardware stores. Make sure you get pure ammonia and that is does not contain detergents. I don't suppose I have to tell you the cheapest source or urea. Add a few drops to the tank each day and test for ammonia and nitrites, when both are clear you can add fish. Do not fully populate the tank on day one, add a few at a time to allow the filters to take up the load. The down side of fishless cycling is that it adds the ammonia as a single blob during the day, so it does not give a natural filter balance immediately, so when you add fish at the end, you still occasionally get an ammonia or nitrite spike, although it is very short lived.

With fish based cycling you add a few tough fish to the tank and wait for nature to take its course. You may need to do frequent water changes for a few days - making sure you de-chlorinate properly. The process of the cycle can be followed by testing for Ammonia and nitrite daily, I don't bother (remember I've pre-seeded the tank), but I do watch the fish carefully, and apply 30+ years of experience. At the first sign of stress I do a water change. When the tank has cycled - i.e. nitrite in zero- which will take a few days if you pre-seed, up to 3 weeks if you don't, you can slowly start to build up the fish numbers. Don't add too many at once or you will stress the newly established filters.

Interestingly, in the old days we didn't cycle tanks, we didn't understand the nitrogen cycle (see Water Changes). In those days we would leave a tank planted for at least a week, and then add the fish very slowly. Where possible I still follow that rule today. Plants from another tank will be covered in the appropriate bacteria, and newly planted plants tend to die back a bit and release Ammonia into the water which kick starts the process.