I have soft water so I don't need to make it softer, which means I have no idea how much RO water costs I'm afraid. Other members do use RO so they'll be able to tell you. You can either buy RO water from a shop (making sure it is plain RO not remineralised) or buy the equipment to make it yourself - though it does waste a lot of water so if you are on a water emeter the cost will add up.
For lowering hardness, it is usual to mix tap water and RO. Half and half will halve the hardness. In your case this would lower it from 14 to 7 dH, which is suitable for most soft water fish. But you would have to use exactly the same mixture at every water change.
For lowering hardness, it is usual to mix tap water and RO. Half and half will halve the hardness. In your case this would lower it from 14 to 7 dH, which is suitable for most soft water fish. But you would have to use exactly the same mixture at every water change.
