Mills Basis A&B is the nutritional foundation of the range: two complementary solutions (A and B) mixed into water to cover the essential macro and micronutrient needs throughout the entire cycle. The Starter Pack bundles several products from the range in smaller formats — ideal for testing the full line without committing to large bottles. In practice, if you're new to Mills and just want to get a feel for it, the Starter Pack is an excellent entry point: it typically includes Basis A&B along with supplements like C4 or Ultimate PK. If you already know you'll stick with this brand, buying separate bottles will be more cost-effective in the long run.

Mills provides a precise dosing chart expressed in ml per litre of water. The calculation is straightforward: multiply the recommended dose (for example 2 ml/L for Basis A) by your total reservoir or watering volume. One thing I often see is growers overlooking the moisture-holding capacity of their medium — an 11 L pot of coco doesn't retain the same amount of water as the same pot filled with soil. I recommend starting at 50–70% of the stated doses on first use, then adjusting based on plant response and EC readings. A conductivity meter is essential when working with Mills: aim for a starting EC of 1.2–1.6 mS/cm during growth, and up to 2.0–2.4 mS/cm during flowering depending on the species.

It's technically possible, but I'd urge some caution. Mills uses specific organic and mineral chelates that can interact with concentrated phosphate- or potassium-based boosters from other brands. The main risk isn't direct burn so much as nutrient precipitation in the solution (white deposits, reduced uptake) or pH imbalance. If you want to combine products, do so gradually — add each product one at a time to the water, mixing thoroughly between each addition, and measure the final EC before watering. In practice, the Mills range is comprehensive enough (C4 for growth, Ultimate PK for flowering) that external supplements are rarely necessary — which is precisely why loyal users tend to stick with it exclusively.

Once opened, a Mills bottle typically keeps for 12 to 18 months under proper conditions. The golden rule: always reseal the cap tightly after use and store away from direct light and excessive heat. I recommend a storage temperature between 10 and 25°C — avoid damp cold spaces (risk of salt crystallisation) as well as overheated sheds in summer. For Basis A and B in particular, avoid any cross-contamination between the two bottles: even a few drops of concentrate A into bottle B can trigger a precipitation reaction. If you notice a deposit forming at the bottom of a bottle after several months, shake it well before use — this is usually normal and does not affect the product's effectiveness.

Mills Ultimate PK is a flowering booster concentrated in phosphorus and potassium, but it is not designed to be used on its own — it's a supplement, not a base. In practice, Ultimate PK is used alongside Basis A&B, which continues to supply the residual nitrogen, calcium, magnesium, and trace elements needed even during late flowering. I typically introduce it from week 3 or 4 of flowering, gradually increasing to the recommended dose, then phasing it out 1 to 2 weeks before harvest to allow for a final flush. C4, another product in the range, can usefully complement Ultimate PK to stimulate flower initiation at the start of the reproductive phase.

Once your Mills solution is prepared, pH should be adjusted last, after all products have been incorporated. Mills tends to slightly acidify the water, which often simplifies the process. The target ranges I recommend are: 5.8 to 6.2 in coco and hydro, and 6.0 to 6.5 in soil. Use a pH-up (potassium hydroxide) or pH-down (phosphoric or nitric acid), adding very small amounts at a time — a few drops are enough for 10 litres. Always measure with a recently calibrated probe: pH strips are not precise enough for working with precision nutrients like Mills. If your pH rises quickly after adjustment, check your source water quality: a high carbonate level (KH) is often the culprit. Osmosis water or lightly remineralised water gives the best results with this range. For more information on deals and promotions on the Mills range, check out the regular offers available at GrowLED.

Mills Basis A&B is the base nutrient I use throughout the entire cycle: it delivers essential macro and micronutrients (nitrogen, phosphorus, potassium, calcium, magnesium) in two balanced parts to prevent precipitation in the bottle. Mills Ultimate PK is a bloom booster concentrated in phosphorus and potassium that I only introduce during the central 3 to 5 weeks of flowering, when the flowers are bulking up.

In soil, I always start with Basis A&B at a reduced dose (50–60% of the recommended dose) because the substrate already provides a nutritional reserve. Ultimate PK comes as a supplement, never as a replacement for Basis. What I commonly see with beginners: they substitute one product for the other and end up with calcium-magnesium deficiencies. These two products are complementary and cover different phases of the cycle.

In hydroponics, the plant relies 100% on the nutrient solution, so I recommend starting cautiously: begin at 50% of the dose shown on the Mills feed chart, then work your way up gradually while monitoring leaf behaviour. For tomatoes in the vegetative stage, I start at 2 ml/L of Basis A and 2 ml/L of Basis B, targeting an EC of around 1.8–2.2 mS/cm.

In practice, the classic beginner mistake in hydro is pushing EC too fast. Tomatoes handle salt excess poorly, especially during growth. I check EC and pH (5.8–6.2 in hydro) with every reservoir change. Mills formulates highly concentrated, readily available products — less is often better to begin with. Browse the Mills range available at GrowLED to get your setup started.

Yes, the Mills range is fully compatible with aeroponics. In practice, I adjust two things: dilution and filtration. In aeroponics, the nozzles spray fine droplets directly onto the roots, so any undissolved particle can clog them. I always prepare my solution in a separate container, agitating thoroughly before feeding the reservoir, and I filter through a 100 µm filter at minimum.

The target EC in aeroponics is generally lower than in NFT or DWC because root uptake is highly efficient: I aim for 1.4–1.8 mS/cm during growth and 1.8–2.2 mS/cm during flowering with Basis A&B. Mills Vitalize (silica-based) is particularly valuable in aeroponics as it strengthens the cell walls of aerial roots, which are more exposed to the mechanical stress of the nozzles.

I introduce Mills Ultimate PK from week 3 or 4 of flowering, once the stretch phase is over and the flower sites are well established. Introducing it too early risks stalling late vegetative development and creating an imbalance with nitrogen.

In practice, here is how I work Ultimate PK into my schedule: I ramp up the dose gradually over 2 weeks (starting at 0.5 ml/L, then 1 ml/L), hold at full dose for 2 to 3 weeks, then taper off before the final flush. If you are growing short-flowering varieties (7–8 weeks), compress the window: 2 weeks ramping in, 1 to 2 weeks at full dose maximum. Do not exceed 1.5 ml/L unless the Mills feed chart specifically indicates otherwise.

Yes, I regularly combine Mills C4 and Mills Vitalize without any root burn issues at recommended doses. Mills C4 is a bloom stimulator based on amino acids, seaweed extracts, and carbohydrates that feeds microbial life in the substrate and densifies flowers. Mills Vitalize is a soluble silica source (orthosilicic acid) that strengthens cells and improves stress tolerance.

What I do in practice: I dilute each product separately in my water before combining them in the reservoir, because silica can react with certain components if added directly to a concentrated product. The combined dose stays within manageable EC levels. However, I never use Vitalize at the same time as Basis A&B without adjusting pH afterwards: silica slightly raises the pH of the solution and can impact iron and manganese uptake if left uncorrected.

Under good storage conditions, an opened bottle of Mills Basis A&B remains effective for 12 to 18 months without significant loss of potency. What I always do: store away from direct light, at a stable temperature between 10 and 25 °C, and seal tightly after each use.

Two-part nutrients like Basis A&B are formulated separately precisely to prevent nutrient precipitation in the bottle. Once opened, the main enemies are oxidation and cross-contamination (never use the funnel from bottle A in bottle B). If you notice unusual sediment or significant discolouration, efficacy may be compromised. For smaller grows, I recommend buying a format that matches your actual consumption rather than the large size if you only run 2 to 3 cycles per year.

If I had to pick one substrate for the Mills range, it would be coco coir — in my experience, it is where the line performs at its best. Coco is an inert substrate that behaves like hydroponics but with a more forgiving ionic buffer for dosing errors. Mills formulated Basis A&B with a calcium-magnesium ratio suited to coco, which is naturally low in these elements and tends to retain calcium.

In practice with coco, I water to run-off (20–30%) to prevent salt build-up and target a solution EC of 1.6–2.0 mS/cm in flowering. Additives like Mills Start (root stimulator) and Mills Vitalize (silica) are especially effective in coco because roots are very active in this well-draining substrate. The range also works well in soil, but doses are reduced since the substrate already contributes nutrients.

The target pH depends on the substrate: 5.8 to 6.2 in hydroponics and coco, 6.2 to 6.8 in soil. I always prepare my full nutrient solution before adjusting pH — never the other way around — because every product I add shifts the final pH of the solution.

My concrete recommendation: add all your Mills nutrients to the water, mix thoroughly, check EC, then correct pH using a phosphoric acid-based pH-down (avoid in late flowering as it adds phosphorus) or citric acid. Make corrections in small increments and allow 1 to 2 minutes to stabilise before re-measuring. A pH that is even 0.3 points off can lock out iron, manganese, or calcium uptake even when your EC is perfect — this is often the real cause behind deficiencies wrongly blamed on the nutrients. Check our Mills range offers at GrowLED to complete your nutrient programme.