Hard vs soft water in the UK

Ask about your own supply

Start with your local water supplier’s water-quality information. Many suppliers let you check hardness using a postcode or supply-area search. A postcode lookup is useful advice, but it does not replace checking a particular grow: treatment, storage and the use of reverse osmosis can change what reaches the reservoir. Record whether the source is tap water or RO water and keep that description alongside the feeding programme. If you cannot confirm hardness, ask the supplier rather than assuming that every address in a county has identical water.

Calcium and magnesium have distinct roles

Magnesium is at the centre of chlorophyll, while calcium contributes to cell wall strength. Monkey Mag Cal combines these secondary nutrients with trace elements. It is particularly relevant in soft water areas, with RO water and in coco. Coco’s high cation exchange capacity can bind calcium and magnesium, so medium choice matters as well as water hardness. This does not give a universal dose for Mag Cal. That dosing detail has not been supplied and should be confirmed with your stockist before use.

Use a range designed for UK water

Grow A+B and Bloom A+B are designed for UK hard and soft water. The supplied chart uses the same stage-based framework for coco, soil and hydro and specifically calls out Mag Cal for coco. That makes the starting point clear without implying that every plant, medium and water supply is interchangeable. Keep your observations alongside the schedule. Avoid changing base feed, water source and several supplements at once if you want to understand which change helped. A consistent record is more useful than a collection of unrelated recommendations.

Check the programme before you start

The Monkey feeding chart is written as a ratio per 10 litres of water. Its headings distinguish vegetative growth, bloom and flush, and the programme toggle selects PK or Resin. Before measuring anything, check that the week on the screen is the week you intended. A veg week and a bloom week can share a number but involve different base feeds. The chart’s ranges should remain ranges in your notes. A displayed interval does not mean that the website has secretly chosen one precise value for your crop. Read the full row and the surrounding programme rather than lifting a number out of context.

The calculator is a convenient way to change reservoir volume without changing the underlying chart. Enter litres, choose the week and programme, and read the millilitres for each included product. If you double the water volume, the confirmed amounts double; if you halve it, they halve. A product without a confirmed dose is not automatically assigned one. This simple boundary is important: arithmetic can scale an instruction, but it cannot supply missing product guidance.