Cal-Mag Explained: When UK Growers Need a Magnesium & Calcium Supplement

Two secondary nutrients, two jobs

Magnesium forms the centre of chlorophyll. Calcium supports cell wall strength. Monkey Mag Cal supplies both secondary nutrients with trace elements. The product is particularly relevant to soft water, reverse-osmosis water and coco growing. Those use cases explain why the bottle exists; they do not establish a diagnosis from a photograph. If a plant looks unhealthy, record the medium, water source, current programme and recent changes before assuming a single nutrient is missing. Several variables can look similar when all you see is a damaged leaf.

Why coco changes the conversation

Coco has high cation exchange capacity and can bind calcium and magnesium. That is why the Monkey feeding chart specifically says to use Mag Cal for coco. A grower moving from soil to coco should not simply copy every previous decision without considering the new medium. Equally, a grower using RO water should make that fact clear when speaking to a stockist. A useful question is not just whether to buy cal mag, but how it fits with the complete base nutrient system, medium and water source already in use.

Confirm the missing dose

A confirmed dose for Mag Cal is not present in the supplied Monkey data. The correct response is to ask your stockist, not borrow a figure from another brand or infer one from bottle size. The nutrient calculator therefore shows confirmed chart products and leaves Mag Cal dosing uncalculated. Keep this distinction clear in your own notes. An accurately measured but unverified recommendation is still unverified. When the brand confirms the missing instruction, it can be added consistently to the product information and schedule.

Read the chart as a complete programme

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.

Keep water, medium and environment in the picture

Monkey nutrients are intended for UK hard and soft water and for coco, soil and hydro. That gives a common framework, but it is still worth describing the grow accurately. Write down your medium, water source and programme so that a conversation with a stockist begins with useful information. For coco, the chart explicitly calls for Monkey Mag Cal. Its dose still needs confirmation, so ask rather than borrowing another brand’s figure. More information is not the same thing as more bottles. Clear inputs and a readable schedule are often the best starting point for a productive question.

The chart also carries environmental reference information. It lists pH 5.5–6.5, temperature 20–27°C, and week-specific EC and humidity values. Normal and closed-room EC are separate rows; do not silently substitute one for the other. These figures belong to the supplied chart. They are not a full diagnosis of every indoor setup. A useful grow record captures what was measured and when, not merely what a target row said. If something changes, that record helps explain the sequence without relying entirely on memory.

Avoid solving an unknown problem with an unknown dose

When advice is missing, keep the gap visible in your own decision-making. A product name, a photograph or a bottle size cannot confirm an NPK analysis or a dilution rate. Monkey’s supplied information deliberately leaves some details open: Mag Cal dosing, Ultra Zyme’s technical instructions and certain size or analysis confirmations. The website hides unconfirmed fields instead of presenting guesswork as a specification. Your stockist can help you obtain the latest confirmed directions. Until then, an honest unanswered question is more useful than a confident invented answer.

Likewise, do not assume every supplement should run throughout every week. Root Shoot, Boost, PK 9/18 and Resin each have their own chart windows. Stress has a consistent role through the twelve growth and bloom weeks, but not a listed flush dose. Monkey Mist is a ready-to-use leaf spray, not a reservoir additive with a scaled millilitre instruction. Keeping these jobs distinct helps the system stay simple. If the crop or timetable differs from the chart, describe that difference before asking for a recommendation.

A practical next step for your grow

Start by opening the feeding chart and checking the programme you plan to use. Then read the relevant product page for its description, mechanism, ingredients and confirmed instructions. Safety data sheets are linked where supplied. A safety sheet is valuable for handling information, but should not be treated as a substitute for the feeding programme. Contact Monkey or speak with a stockist if something is unclear. The range was developed by UK growers with more than two decades of nutrient-industry experience, with more than two years of development and testing before its 2021 launch.

The aim is a system that growers can understand, trust and use with confidence, not a bottle for every unexplained problem. Choose a starter or expanded kit around an understood role, retain the correct programme and measure the actual reservoir volume. Keep your notes straightforward enough that you can explain the grow to somebody else. That is science made simple in practice: accurate information, a consistent schedule and no invented shortcuts. UK born. Grower led. Built from experience.

Before buying, separate confirmed availability from the product description. There are no published prices in this catalogue, and a size listed for one product is not automatically a size offered for another. Root Shoot sizes require confirmation, while Monkey Mist sizes are not supplied. Ask your stockist about the product and size you actually need. A website photograph can help identify a bottle, but does not override the current verified product information.

A good question to Team Monkey includes the product name, whether the grow is in veg or bloom, the medium and the water source. If you are asking about the chart, include the programme and reservoir litres too. Those details make it easier to keep the answer connected to your actual grow. Do not turn advice for a different stage into a new instruction without checking it. The system is intended to stay understandable from start to finish: roots, shoots and fruits, with health-support products used for clear, distinct purposes.