Mills Nutrients and Bloom
Mills on the left, Bloom on the right, matched on the job each bottle does. Basis A and B stays at the heart of it. Here’s what Bloom brings either side of their stimulators.
Last checked 5 November 2026 · Public information only
This Fit Report is a summary of publicly available information about Mills Nutrients and its products, taken from their own website, labels and published material as of 5 November 2026. We’ve linked each source so you can check it yourself. Rates are as printed on each company’s own pages; we don’t show prices. It isn’t affiliated with, endorsed by or approved by Mills Nutrients, and product names belong to their owners. Products, rates and claims change, so please confirm current details with the manufacturer before making any decision. Spotted something out of date? Email nathan@bloomyellowbottles.com and we’ll correct it.
Four bottles and a chart, and the gaps around them.
Mills keeps it tight: Basis A and B, Start-R early, C4 from flower week 2, Ultimate PK booster from week 5, plus Vitalize and CalMag. There’s no standalone kelp, fish, humic or sea-mineral bottle, no flip additive and nothing for the flush week. That’s where Bloom’s weekly bottles sit.
- Stays as is: Basis A and B, Mills pH+ and pH-, and Mills substrates.
- Both have one: early-stage, mid-flower, late-bloom, silica and cal-mag bottles.
- Not on their list: kelp, tuna, humic, sea minerals, a flip additive, a finish and foliars.
Where the programs complement each other
Kelp, tuna, humic and sea minerals around Basis
Mills’ Regular line has no standalone kelp, fish, humic or sea-mineral bottle. Seaweed, Seafuel, Humate and Sea Minerals go in at 0.13–2.5 ml/L weekly, at the stimulant step of Mills’ own mixing order.
Ultra in flower weeks 1–2
Start-R finishes and C4 starts in flower week 2. Ultra covers weeks 1–2 at 1 ml/L weekly. Watch EC in week 2 where they overlap (our read).
Final past Mills’ week 9
Mills’ chart ends at flower week 9 with no flush column. Final runs 1 ml/L weekly over the last two weeks, including the flush.
Why each one fits
What the Bloom product does, the research behind that kind of input, and where it sits in a program that already runs.
Kelp and tuna next to Basis
What it does. Seaweed is southern bull kelp; Seafuel is tuna and kelp. Both run at 1 ml/L weekly: Seaweed from seedling through the flush, Seafuel from clone through late flower, tapering at the flush.
Reviews of seaweed extracts report effects on growth and stress tolerance across many crops. Work on protein hydrolysates, which fish inputs belong to, is newer and links them to nutrient uptake, mostly under stress. None of it tests these bottles or cannabis.
Ali et al. (2021), Plants (review) · Malécange et al. (2023), Int J Mol Sci (review)
How it stacks. Mills’ mixing order is Vitalize, Basis A, Basis B, then one stimulant at a time, mixed through, then pH. Our read: Bloom’s bottles go in at the stimulant step, one at a time.
Humic all the way through
What it does. Humate is 10% humic acid at 2.5 ml/L weekly, seedling through flush. Sea Minerals is trace minerals from sea water at 0.13 ml/L weekly, veg to bloom.
A major review links humic substances to more lateral roots and to root changes tied to nutrient uptake. It doesn’t test either company’s products.
How it stacks. C4 lists humic acids and runs flower weeks 2–6. Humate covers veg and late flower either side of that, so plan total humic across the run (our read).
Ultra before C4 kicks in
What it does. Ultra runs 1 ml/L weekly in flower weeks 1–2. It’s a timing tool, so there’s no study cited for it here.
How it stacks. Start-R finishes at flower week 2 and C4 starts there at 0.5 ml/L. Ultra sits across those two weeks; watch EC in week 2 where they meet (our read).
Final for the last two weeks
What it does. Final runs 1 ml/L weekly over the last two weeks, including the flush, alongside Ooze. Ooze is plant extracts, fulvic acid, vitamins and amino acids at 2.5 ml/L weekly from flower week 5.
How it stacks. Mills’ chart stops at flower week 9, with Basis dropped to 2 ml/L and no flush column. Final carries on through the flush. Ooze shares weeks 5 to 9 with Ultimate PK booster, so plan that stack.
Their line, Bloom’s fit at a glance
Matched on job, not NPK. Mills and Bloom both print ml per litre; Mills’ rates come from its growth chart, Bloom’s from its weekly feed chart. Tap a tag to filter.
Keep your base. Mills’ chart says always use A and B equal.
Mills sets pH to 5.5–6.5 last. Bloom has no pH product.
Bloom makes no growing media. Its bottles run in soil, coco and hydro.
Same early window. Mills’ page lists no ingredients for Start-R. Pick one or plan the stack.
C4 runs 0.5–1.5 ml/L to week 6 on their chart. Same window as Phat and SWTNR.
Both sit at peak bloom. Mills’ runs to week 9; Bloom’s PK is as needed. Plan one.
Both are silica, both go in first. Run one.
Same job, similar rate. Mills’ is aimed at soft or RO water. Pick one.
C4 starts at week 2. Ultra covers the first two weeks of the flip.
Southern bull kelp, and a tuna and kelp tonic, through the cycle.
Humic only shows up inside C4, flower weeks 2–6. Humate runs start to finish.
Trace minerals from sea water, on top of Basis.
Mills’ chart ends at flower week 9. Final runs the last two weeks, including the flush.
Foliar sprays for veg and the flip, outside the feed line.
Where each bottle sits in the cycle
Mills Nutrients’s timing in grey, Bloom’s in yellow, across shared stages of the grow.
| Stage | Root | Veg | Flip | 3–4 | 5+ | Last 2 | Flush |
|---|---|---|---|---|---|---|---|
| Mills Nutrients, per their pages | |||||||
| Start-R | |||||||
| Basis A · Basis B | |||||||
| C4 | |||||||
| Ultimate PK booster (Mills) | |||||||
| Vitalize | |||||||
| CalMag (Mills), as needed | |||||||
| Bloom, per Bloom’s weekly feed charts | |||||||
| Roots | |||||||
| Pre | |||||||
| Ultra | |||||||
| Phat (weeks 3 and 4) | |||||||
| Ooze (wk 5 to flush) | |||||||
| Final (with Ooze) | |||||||
| Seafuel | |||||||
| Seaweed · Humate · Sea Minerals | |||||||
| SWTNR | |||||||
| Cal-Mag | |||||||
| Groigen (foliar, as needed) | |||||||
| Florigen (foliar, as needed) | |||||||
| PK (as needed) | |||||||
| Silica | |||||||
Timing comes from Mills’ Regular growth chart (tap water: two start weeks, then nine flower weeks, no flush column) and its product pages. C4 starts at flower week 2 and stops after week 6, so its edges are pale. Vitalize drops to 0.1 ml/L in weeks 5–6 and stops. CalMag is used as needed for EC or weekly as a preventive, so it’s pale (our read). Bloom’s bars follow its weekly feed charts; pale Bloom bars are tapers or as-needed bottles.
Put it side by side
Where both ranges have a product for the same job, the fair answer is a test in your own room. Here’s what to watch and how to keep it fair.
Keeping it fair
- Same plants. Clones off the same mother, same cultivar, same age.
- Same room. Same light, climate, media, pot size and watering.
- Same base. Keep the base feed and EC the same on both sides.
- One change. Change only the product being tested, and write down what you see each week.
Already covered
- Base feed. Basis A and B, equal parts, veg through flower.
- Early and mid-flower stimulators. Start-R and C4.
- Late bloom. Ultimate PK booster from flower week 5.
- Silica, cal-mag and pH. Vitalize, CalMag, pH+ and pH-.
Stays exactly as is
- Basis A and B. Bloom’s additives go in around it.
- pH+ and pH-. Bloom doesn’t make pH adjusters.
- Mills substrates. Bloom makes no growing media.
- Start-R, C4, Ultimate PK booster, Vitalize and CalMag. If they’re working in your room, keep them, or test Bloom’s next to them.
Background, science and sources
Who Mills Nutrients are
Mills Nutrients BV is a Dutch nutrient brand. It calls its range bio-mineral, mixing organic and mineral sources, and points to twenty years of lab research and grow experience. Its site doesn’t name a founder.
The Regular line is Start-R, Basis A and B, C4 and Ultimate PK booster, with Vitalize, CalMag and pH+ and pH- alongside. Mills also has an Organics line, solid nutrients and substrates. Its online shop serves several EU countries, and it names Hydrofarm in Shoemakersville, Pennsylvania as its official US distributor.
Sources: About · Full range · US distributor
What each company brings
Mills Nutrients: A two-part base, an early-stage additive, a mid-flower stimulator, a late-bloom booster, silica, cal-mag, pH adjusters and substrates, with growth charts for tap and RO water.
Bloom: one additive for each stage of the crop, seaweed, humic and sea mineral inputs, foliar sprays, and weekly feed charts for soil, coco and hydro. Rates and timing are on every product page.
Cropping Solutions, the other brand under Agricultural Organics, isn’t part of this report.
Dose basis: how each side counts
Mills’ growth chart prints ml per litre for each week: Basis A and B ramp from 1 to 4 ml/L each on tap water (up to 5.5 on RO), Start-R 1–2 ml/L, C4 0.5–1.5 ml/L, Ultimate PK booster 2–2.5 ml/L and Vitalize 0.2 then 0.1 ml/L. CalMag is about 1 ml/L to lift EC, or 1 ml/L once per week as a preventive.
Bloom prints ml per litre too, on a weekly feed chart. Mills’ chart doesn’t say how often to feed, so the same number on each side isn’t always the same weekly amount.
Mix calculator
Rates as printed on each company’s page (1 US gallon is 3.785 L). Bloom’s rates are per litre of nutrient solution, dosed weekly per its feed charts. Pick a product and your tank size.
SiliconEmerging
A 2017 editorial in Frontiers in Plant Science says silicon is widely studied for stress tolerance, but there’s still no conclusive evidence on exactly how it works.
Why it matters here: Vitalize and Bloom Silica do the same job and both go in first. The science backs silicon as an input with open questions, so run one silica product (our read).
Deshmukh, Ma and Bélanger (2017), Frontiers in Plant Science (editorial)
Potassium late in the runWell supported
Hasanuzzaman and colleagues (2018) review potassium’s roles in plants: enzyme activation, stomatal control, photosynthesis and stress tolerance.
Why it matters here: Ultimate PK booster and Bloom PK both sit in late bloom from week 5. The review covers potassium as a nutrient, not either bottle.
Sources, all viewed 5 November 2026
Mills Nutrients: Home · Growth charts · Full range · Basis A · Basis B · Start-R · C4 · Ultimate PK booster · Vitalize · CalMag (Mills) · About · US distributor
Bloom: Roots · Pre · Ultra · Phat · Ooze · Final · Seafuel · Seaweed · SWTNR · Humate · Cal-Mag · Groigen · Florigen · Sea Minerals · PK · Euro · Grow · Flower · Silica · OrganiShield
Last checked 5 November 2026. Public information only. Not affiliated with, endorsed by or approved by Mills Nutrients; product names belong to their owners. Please confirm current details with the manufacturer. Corrections: nathan@bloomyellowbottles.com. All Fit Reports