Problem with Ammonia

[Just Toby]

You don't have to but it is good for the fish, I use RO Right from Kent Marine to do this usually about twice a month.

Ro water without the added mineralization is very unstable as it has no buffering capacity and the ph will move massively. IMO you should not put raw ro in a fish tank.

The reason this is not talked about so much is that the majority of ro is used in marine tanks and therefore mixed with quality salt which contained the minerals. You can use it neat as a top up following evaporation as only pure water evaporates and the minerals are left behind.