It seems pretty trivial: water is poured in the aquarium. Sometimes, though, things can be a little more complicated than what can be assumed at first sight, since tap water contains calcium, carbonates, nitrates, phosphates and often many other substances, meanwhile only pure H2O evaporates from our aquarium. The water composition is, depending on geographical location, fairly variegated. Calcium, carbonates and magnesium are warmly welcomed, because such compounds are extensively used in a reef aquarium. In the case of nitrates and phosphates such fact can assume a different aspect. Of course, they are of crucial importance for vegetal organisms, but an increment in quantity in the aquarium’s waters would be quite bothersome. But that is exaclty what happens, if we substitute evaporated water with normal tap water containing nitrates, on a daily basis. If our mains water shows a nitrate content of beyond 20/mg/l, it definitely is not to be employed without previous treatment. For such pre-treatment, total demineralization is adapted with the use of ion exchanging resins, or an reverse osmosis implant, an option that ever frequently replaced resin implants over the last several years. With these devices we can get a very clean water, though containing yet a little bit more than just H2O, which has evaporated from our aquarium, since the substances are not 100% removed. But this can anyway be a big step in the right direction, since the remaining quantities of such substances are insignificant. Another possibility consists in the use of pure spring water available in several locations. Even in this case, though, attention is to be payed concerning the content of nitrates and phosphates.
Automated or not?
How often should evaporated water be replaced? Continuously is better, since evaporation naturally leads to a change in the aquarium’s saline content. Indeed, the optimal solution consists in automation, with the use of a simple device easily available on the market. This device can also be operated once every two hours thanks to a timer, in order to make it function for fifteen minutes and replace the evaporated water, then shutting it down. This way, functioning time can be reduced, as well as the risk of malfunctions. Those who would want, or would have, to operate the substitution manually, can also utilize a simple bucket. In the case of an open aquarium with a strong evaporation a daily substitution is to be advised; in a closed aquarium (featuring neon lamps) with a reduced evaporation only one substitution twice or three times a week is going to be sufficient.