In order to keep fish successfully in your home aquarium it's important to have good quality water. Many beginner aquarists think that water is just water - it all looks the same, right? In fact, it varies a great deal. Understanding how and why will help you to keep your aquarium in much better condition.
The sensitivity of fish, plants and invertebrates to water quality varies. Some are very hardy and can cope with quite a bit of pollution, but even the most delicate fish should not sicken and die as often as they do due to poor conditions. Good quality water does require ongoing maintenance, so think about this when you set up your aquarium equipment and choose your fish. Don't buy delicate fish if you can't make an ongoing commitment to monitor, clean and generally care for their environment.
Natural PollutantsNo matter how clean the water you originally use for your fish, in time it will become polluted. This is because fish produce waste products just as humans do. These can build up in the water, making it both unpleasant and poisonous, with rising ammonia levels. The natural biochemical cycle of an established tank will break them down into less problematic compounds, but sometimes this cycle gets overloaded. If your tank is overcrowded or if you have too few plants or too much of the wrong sort of algae, the ecosystem can slip out of balance, resulting in dangerous levels of pollution. This can make your fish more vulnerable to disease and has the potential to kill them.
Natural pollutants can be effectively removed using filtration. Your tank will support more fish in healthy condition if you have a more effective filter system, but filters need to be cleaned from time to time too, so make sure you choose the right one for your aquarium's needs and for the level of maintenance you're prepared to commit to. You should also be prepared to clean the aquarium by hand every one to two weeks, scraping off algae from the sides and siphoning the gravel. The latter is especially important if you have an undergravel filter, as these suck particles of waste down through the gravel and some inevitably get stuck, building up to problematic levels over time.
Water ChangesMost aquariums benefit from regular partial water changes. You should never change all the water at once, as this will kill the beneficial bacteria which sustain your aquarium's ecosystem, and it will also put your fish at risk of shock due to changes in the water chemistry. A good basic rule is to change about a fifth of the water per week. If you have delicate fish, add new water slowly so as to reduce the risk of shock.
Learning how to look after an aquarium will make you think again about the quality of the water which comes out of your taps. You should never put fish into pure tap water, as it usually contains chlorine (and often fluoride) which, though hardier fish can sometimes survive it, will cause them a lot of pain and stress. Leaving water to stand for an hour will get rid of these chemicals but will not do anything about other pollutants, so it's best to treat the water with a commercial product designed for the purpose, such as Interpet Fresh Start or Tetra Aquasafe, before adding it to the aquarium.
What other pollutants might you expect to find in tap water? The most significant are heavy metals. This is particularly problematic if you have old plumbing with lead pipes which gradually leach lead into the water, but there are some heavy metals present in almost every water supply. Most commercial water conditioners will bind these into non-toxic molecules, keeping your fish safe.
Looking after the water in your aquarium isn't always an obvious issue as, until things start to go really wrong, problems aren't usually visible. But making the effort to provide good general maintenance and monitor water chemistry will pay off by helping you to keep happy and healthy fish.