Is using distilled water for an aquarium advised?

No, I would not advise using distilled water in aquariums, most aquarium fishes need some level of mineralization in their environment. Distilled water does not exist in nature, putting fish in distilled water would mean subjecting your pets to an environment that they have most likely not genetically evolved to live in. read more

You can buy pH buffers, but it's much easier if you use RO or distilled water for every other partial water change. It may be necessary to adjust water types based on pH readings. Usually, pH decreases slowly as an aquarium matures. read more

Once the water is distilled it will contain no beneficial minerals or salts, it is alright to use this water when topping up the aquarium to compensate for evaporation losses but do not use this pure water for water changes or for filling the tank. read more