RO units are otherwise called 'Reverse Osmosis Systems' and are the easiest way to provide your tank with water that is free from chlorine, nitrates, phosphates and heavy metals that can damage your aquariums delicate ecosystem.
They convert tap water into what is commonly referred to as 'RO Water', which implies that the water has undergone a purification process to rid it of minerals and substances that are detrimental to your tank's health.
If you don't purify your water and just add tap water to your tank, it means algae blooms are far more likely to form, costing you a little more money in terms of additives and treatments to get rid of it, although fortunately Swell UK keep the cost of these low too.
Buy your new RO unit from Swell UK before 3pm weekdays and you can enjoy our Next Working Day Delivery options on top of great prices!