Mills Nutrients Basis A&B (Hard Water) — Two-Part Organo-Mineral Base Nutrients for UK Growers
Best for: Hard water growers wanting a reliable, easy-to-use two-part nutrient system that works across soil, coco, and hydro without the premium price tag
Our thoughts
This is a solid workhorse nutrient system. Mills Basis A&B Hard Water does exactly what it should — it's formulated specifically for UK tap water, it's straightforward to use, and it doesn't overcomplicate things. If you're running hard water and want a two-part base that covers veg and flower without faffing about, this is one we recommend regularly to growers who want results without the faff.
Mills Basis A&B (Hard Water) is a concentrated two-part organo-mineral base nutrient designed specifically for growers in hard water areas. It combines mineral salts with organic additives — giving you the control of hydroponics with the forgiving nature of organic growing. The hard water formulation is pre-balanced to handle high calcium and magnesium content in your tap water, which means you're not fighting nutrient lockout before you've even started. Works across all growing media: soil, coco, and hydro. One system, all stages, all methods.
How it compares
This sits squarely in the mid-range two-part nutrient market — proper kit at sensible money.
- Organo-mineral blend means fewer nutrient buildups than fully synthetic systems
- Hard water formulation gives you an advantage UK growers don't get with standard A&B kits
- More forgiving pH range than competitor systems — easier to dial in
- Requires double the dose of some competitors, but that's reflected in the pricing
Against General Hydroponics FloraDuo or Advanced Nutrients, you're trading slightly higher dosing for lower cost and UK-specific water chemistry. Against CANNA, you're getting simpler mixing with less faffing between veg and flower bottles.
Usage guidance
Mills Basis A&B is straightforward, but mixing order matters:
Mixing your nutrient solution
Never mix parts A and B together dry. Add Part A to your water first, mix thoroughly, then add Part B. Use equal parts of both — scale your dosing rate from 1ml per litre up to 3.5ml per litre depending on plant stage and feeding strength.
For vegetative growth
Run lighter feeds in early veg (1-1.5ml/L), then build strength as plants establish. The blend promotes healthy root development and strong stem growth without pushing unnecessary flowering signals.
For flowering
Maintain full strength (2.5-3.5ml/L) throughout. The A provides calcium and red iron for structural support; the B delivers magnesium and other essentials for resin and material production.
Across different media
Works identically in soil, coco, or hydroponics. Hand-fed pots, drip systems, or full flood tables — the nutrient blend performs. Coco and hydro growers should run feeds to mild runoff; soil growers can feed slightly lighter and let the medium buffer naturally.
pH management
Target pH 5.6-6.2 in hydroponic systems. The hard water formulation handles alkaline tap water better than soft water formulas, but you'll still want to check and adjust depending on your actual water source.
Storage
Keep both parts in a dark, cool place. Concentrate will last years if stored properly — no special fridge needed.
Technical specifications
- Format: Two-part concentrate (A & B)
- Available sizes: 1L, 5L, 10L
- Dosing rate: 1–3.5ml per litre (equal parts A & B)
- Type: Organo-mineral NPK base nutrient
- Nitrogen (N): Dual-source formulation
- Phosphate (P₂O₅): 4.1% w/w
- Potassium (K₂O): 2.7% w/w
- Calcium (Ca): 4% (Part A)
- Magnesium (MgO): 0.7% (Part B)
- Iron (Fe): 2% red iron (Part A)
- Sulphur (SO₃): 1.4% w/w
- Trace elements: Boron, copper, manganese, molybdenum, zinc
- Active ingredients: L-amino acids, humic & fulvic acids, root enhancers
- Target pH: 5.6–6.2 (hydroponic systems)
- Formulation: Hard water (EC starting point >0.3)
- Media compatibility: Soil, coco, hydroponics, all watering methods
Who this is for
- Growers in hard water areas tired of fighting mineral buildup and pH swings
- Two-part nutrient users who want simplicity — no switching between veg and flower bottles
- Hydroponic, soil, and coco growers wanting one system that works across all media
- Budget-conscious growers who don't want to pay premium brand markup for solid results
- Intermediate growers ready to move beyond all-in-one feeds but not ready for complex multi-part systems
- Growers in the UK and Europe where hard tap water is standard
Not ideal for soft water areas — grab the soft water version instead. Also not the best choice if you want pre-balanced veg and flower bottles (that's where CANNA's system has an edge).
Our take
Mills Basis A&B Hard Water is what a good two-part nutrient should be: simple to mix, forgiving across media, and actually designed for the water that comes out of UK taps. It's not the cheapest per ml, but you're paying for a system that works without drama.
The organo-mineral blend means less nutrient salt creep, the hard water formulation saves you pH headaches, and it delivers results across veg and flower without needing a new bottle every eight weeks. Worth picking up while this stock lasts — particularly if you've been fighting hard water nutrient lockout with generic systems.
