Using RO water

RO, Reverse Osmosis removes most of the suspended solids from water therefore lowering the GH (General Hardness), KH (Carbonate Hardness) and slightly reducing the pH as a result. It is not exclusively for marine aquariums and has many benefits in freshwater.

Situations where it is often used:

• RO removes nitrates from the water so can be used where tap water contains nitrates.
• It is most often used in hard water and high TDS areas making lower TDS and softer water allowing people to keep fish adapted for softer water.
• Used where heavy metals might be present in the tap water.
• To top up from evaporation where mineral concentrations will gradually increase resulting in what is known as old tank syndrome.

How to treat RO

RO is void of any minerals that are beneficial for fishes and therefore must be remineralised with the minerals desired. This can be most easily done by mixing a proportion of the RO with tap water to reach your desired TDS. It can also be done with minerals such as Tropic Marins for remineralising. Any minerals should include a full range to cater for the fish.

RO does not need to be dechlorinated unless being mixed with tap water as the RO process removes chlorines and chloromines.

Using rainwater

This is best really left for areas with lower population levels due to air pollution. So I would recommend really thinking about where you live. It is also recommended to have a clean roof but not cleaned with chemicals that could influence the rain water.

Rainwater is also void of nutrients and minerals so depending on the fish you keep it is worth considering remineralising.

It can be collected from a house, shed or greenhouse gutter into a water butt. It is recommended to keep the gutters clean therefore.

Removing leaves or any large matter that will enter the water is recommended with a grid of some kind.

Using activated carbon to treat the water might be worth considering to remove possible traits of air pollution although it will not be a solution to an area with high air pollution.

Unless mixing with tap water there is no need to dechlorinate.