Water: the essential element for fish
On a very basic level water is 99.98% H2O in a liquid that your fish swim, eat, breathe and excrete into. What about the other .02%? Is it important? Of course it is. It is these minute quantities of dissolved gases and dissolved solids that makes all the difference in whether the water is hospitable or poisonous to the fish. It is this 0.02% of dissolved substances that make sea water, river water and lake water different from each other. Note that seawater has a much higher level of dissolved salts of around 3.5%. It only takes minute quantities of the common gases such as ammonia, carbon dioxide or insufficient oxygen to poison or drown fish. Likewise it only takes a small amount of pollution or the wrong type of chemical to be dissolved in the water to poison and kill fish. But when conditions are just right or within reason then your fish will thrive without much care from you.
Creating a generic biotope for your fish to live in
As a fish keeper is is your responsibility to recreate a reasonable biotope for your fish that is as close as possible to the fish’s natural environment as you can.
Water has dissolved gases such as oxygen, carbon dioxide, nitrogen, ammonia and chlorine. Some of these gases are poisonous while others are necessary for fish to breathe. Water also contains dissolved minerals that determine the general hardness of your water. Some fish thrive in very hard water with a high ph, while other fish prefer much softer water with a lower ph. Organic matter can also dissolve in the water, usually darkening the water and acidifying it.
A biotope should include a substrate, plants and a source of light with the temperature of the water kept within a suitable range for the plants and fish. The choice of subrate includes gravel, sand, and even soil. Soil is usually topped with gravel. Other less essential features you might want to include in your fish’s biotope could include rocks, roots and branches.
Is tap water safe for fish?
Tap water direct from the tap is not suitable for use in an aquarium. The main problem is chorine which water companies put in the water to kill off any potential bacteria in the water. To remedy this you need to leave your tap water standing in a container for at least 24 hours. This allows the chlorine to evaporate. This can be achieved by using buckets of water or water barrels to store the water.
Another danger to your fish is from dissolved copper which can come from copper pipes. Water that comes into contact with copper will slowly absorb the copper. This problem is worse for new copper pipes. But this can be remedied by running your tap water for a few minutes until uncontaminated water starts to come through. Copper is poisonous and even copper coins left in your aquarium will slowly dissolve and kill your fish.
If you are going to be serious about the quality of your fish’s water then you should buy a water test kit. A good test kit will test ph, ammonia, nitrite and nitrate as well as general hardness.
If you are a new fish keeper who wants the best chance of keeping your fish healthy and alive then test your tap water before you buy any fish. When you know the ph and hardness of your water then you can buy fish that prefer the water from your tap. Adjusting your water to suit fish that like a different type of water is best left to the advanced aquarist who don’t mind the extra effort. Some fish when kept in the wrong type of water will simply die after a few weeks and certainly won’t thrive.
If you are a more experienced aquarist then you can start adjusting the ph and hardness of your tap water so that you can keep the more delicate species of fish. To soften your water you can buy a reverse osmosis device that will remove the minerals from your water. Such water is usually too soft and must be mixed with unfiltered tap water to achieve the correct level of hardness. You can also use rainwater collected from a safe source.
To adjust the ph of your water you can either use a muslin bag containing peat moss to acidify your water or you can use calcium carbonate sand to alkalinify it instead. In order to reach the correct ph level.
All these procedures are complicated and time consuming and even prone to error. Messing with your tap water usually means you will have to monitor changes in your water conditions to maintain it. To make this complicated process a little easier it is best to prepare large batches of water in say a 200 litre barrel all in one go and then draw off water as needed.
I recommend that you don’t bother with all this messing around and just buy fish that can do well in the water that comes from your tap. There is usually quite a variety of fish that will suit your water conditions but you may have to avoid a particular species of fish that you might be keen on.
What water conditions are best for fish?
Normally the ph used in most freshwater aquaria ranges between 6.0ph and 8.3 ph. However Lake Tanganyika fish like an even higher ph, even as high as 9.0ph. And they also like hard water. Ph nearly always varies together with hardness. High ph above 8.0 usually means very hard water, while low ph of 6.4 or less coincides with soft water. Some amazonian fish like water that is of a ph less than 6ph and have very soft water.
Most of the commonly available fish in your aquarium prefer an average ph around 7ph and a medium level of water hardness. Not only that but such species can also tolerate a wider variation away from this medium than other more exotic species. Tank bred fish that have been bred in aquaria for several generations are overall more adaptable to variations in aquarium conditions compared to their wild caught counterparts.
Most average species will live in a wide range of possible water condititions. However, when it comes to breeding the ph and hardness must more closely resemble the fish’s conditions in the wild. Only then will some fish be capable of breeding and their eggs hatching.
This is a measure of the amount of dissolved minerals in your fish’s water. The most common minerals are calcium, magnesium and sodium.
These dissolved minerals are also essential for the health of your fish and plants.
Most cyprinids, tetras, rasboras and similar river fish like soft water. Most livebearers, Malawi fish and Tangayikan fish prefer quite hard water.
Plants also show a similar type of preference for different levels of hardness depending on the plant species.
Iron for fish health
Plants require minute levels of dissolved iron for optimum health as do fish. Fish acquite iron from their diet while plants will absorb it directly from the water. Pure iron quickly rusts in water making it unusable for the plants and animals. Feeding fish iron rich fish food will not only provide iron for the fish but allow the fish to provide manure that is rich in iron for the plants use.
Dissolved oxygen in water that fish breathe
Dissolved oxygen is essential for fish to breathe. The main source of oxygen in an aquarium is through the surface of the water. So a large surface area of water is essential to allow sufficient oxygen to dissolve into the water to replace the amount of oxygen that the fish breathe in through their gills. Also excess carbon dioxide that the fish release into the water from their gills has to be released from the water through the surface of the water. Plants also give off oxygen when they are in bright light, but will release a small quantity of carbon dioxide at night.
It is best not to rely on the quantity of oxygen that plants produce during the day to supplement the amount from the surface because this source of oxygen stops at night. If you see your fish gasping for air very early morning this is a sign that there is not enough oxygen and too much carbon dioxide in the water in the night so you will have to reduce the number of fish in the aquarium. This can also be a sign you have too many plants.
Fish waste in water
One lethal cause of fish deaths is ammonia poisoning which burns the skin and gills of the fish while also displacing oxygen in the water. Ammonia comes from fish waste and from decaying fish food and other decaying organic matter. In a new aquarium there will be no ammonia but this will build up over the fish few weeks. If you are new to fish keeping you will see your fish as being fine for the first week and may not realised that the fish are slowly but surely poisoning themselves in their own waste matter.
To overcome this you need some way to remove the ammonia as it gets created. You will have to for the first 6 weeks have to do daily water changes, use a filter and make sure that you under stock your tank until it is mature. Also avoid any uneaten fish food being left in the tank that will quickly rot and cause an ammonia spike.
A filter is not just for removing particles from the water but also for providing a base for the growth of bacteria that digest ammonia converting it into nitrite which is also poisonous. Later on another set of bacteria develops that will digest the nitrite converting it into nitrate which is much less harmful. This process takes between 4-6 weeks from new. So partial water changes are needed daily until the filter matures.
This is better explained in cycling your aquarium
Plants take up nitrate but usually not enough so you will need to keep doing partial water changes, perhaps once a week. 10% of the water changed is a reasonable amount of water change.
During this filter maturation period you should test your water daily with a test kit and if the ammonia or nitrite reading becomes particularly high then you will have to do another partial water change to bring it down to acceptable levels.