One common question that we receive about setting up new aquariums is about the most basic ingredient to the aquarium, the water that goes into it. There are a lot of terms that can get confusing when someone is trying to determine how to fill their aquarium and from what source. The options can be staggering – tap water, bottled water, prefilters, and so on – and starting with the right foundation can make all the difference, from the smallest betta bowl to the largest reef system.
This is probably the easiest and most accessible water source in most areas. Whether you get your water from a municipal water sources or from a well, it doesn’t get much easier than going to the nearest sink to fill your bucket or tank. Its ease is definitely a benefit, but keep in mind that municipal water sources will usually contain chlorine or chloramine to kill bacteria and well water sources may contain phosphates or other organics. Tap water can be used, but should be treated or purified to remove these materials before it goes into your aquarium.
Reverse Osmosis (RO) and De-ionized (DI) Water
RO/DI Units are very popular among aquarists. Although Reverse Osmosis and De-ionization are different processes, they are often done in conjunction and in combination filtration systems. In these units, water is forced through a membrane (RO) and through resins (DI) that remove minerals and compounds leaving the water very pure. A unit can be installed to filter tap water and make it safe to use for aquariums, but does not, in itself, remove chlorine and chloramine compounds used in tap water purification. Most newer RO/DI units have carbon prefilters to remove chlorine and chloramine before it gets to the aquarium. While RO/DI filtration removes most of what an aquarists does not want in their water source, it can also remove some of what one does want so RO/DI water must be buffered and “remineralized” before being used. Reef aquarists are the most common RO/DI users and since they use salt mixes before using the RO/DI water, they usually do not have to be concerned since the salt mix itself makes the water suitable for usage again. Anyone using RO/DI in a freshwater system would need to remineralize their water using a buffer appropriate to their system.
Distilled water is one of the purest water types available. It is created by heating water and collecting the pure water that evaporates as steam while leaving solid impurities behind. This is not usually used by home aquarists since it tends to be expensive and more inefficient when it comes to tank maintenance, but distilled water is available in most grocery stores. Most often, it is questioned as a possible water source for smaller tanks like bettas, goldfish and community tanks and by new aquarists looking for an easier and “safer” solution.
Not necessarily. Since it is very pure and has had even more minerals and compounds removed than other processes, it is extremely soft and has no buffering capacity or mineral composition. As with RO/DI water, these minerals are often replaced if the distilled water is mixed with salt mixes for reef systems but it would need to be buffered before it can be used for freshwater or for a small system like a betta bowl. Without being buffered, the water chemistry parameters like pH can fluctuate wildly. For these smaller tanks and bowls, distilled water can be costly, inconvenient and even unsafe.
Spring Water and Bottled Water Sources
Bottled water is popular for those with small tank and for betta enthusiasts. Since it is available in most grocery stores and can be more convenient than dechlorinating tap water, many turn to bottled sources and different brands of spring water for quick water changes. While most spring water is filtered and safe to use, every brand is different and meets different standards. Most bottled water is filtered by reverse osmosis, deionization or distillation similar to the sources already discussed, and many brands add minerals back into the water to improve taste and nutritional value. “Spring water”, by definition, comes from an underground source and its mineral composition is affected by that source so its mineral make-up can vary as a result as well. It is a good idea to test a new brand for pH, hardness, phosphates, nitrates and other base readings before use, especially in a sensitive reef system.
Although the water sources may vary, the requirements of the fish, plants and animals we keep generally does not. If you have questions about how to make your water appropriate for what you want to put into it, feel free to let us know!
Spring water on Mackinac image referenced from wikipedia and originally posted by DaemonDivinus
Water sampling image referenced from wikipedia and originally posted by Alloquep