HydroTops Solo is specifically manufactured for use in conjunction with soil, it’s been formulated and manufactured in the UK with our water in mind. If your using water from your tap, you’re best off using the hard water variant. If your municipal water supply is soft water or you’re using an Reverse osmosis filter, use the soft water variant.
The hard water variant has been manufactured with water that’s got a high amount of calcium and magnesium carbonate dissolved in solution, as in found in most of the UK. Some areas have soft water such as Cornwall, Wales, Scotland and northern English counties. If you find yourself in a soft water area, HydroTops have formulated their soft water range with higher amounts of calcium and magnesium to account for the lower base line levels. Growers in soft water areas may have results that are easier to replicate as they are not reliant on the magnesium and calcium levels stability in the tap water.
Use a reverse osmosis filter and the soft water type of nutrients to completely remove a variable water source, since r/o water has no compounds dissolved in the solution it will have the most dependable results due to the constant variables.