Short version? Get Grow Genius Mono Silicic Acid. It's pH neutral and the dose is tiny, 0.3ml per 10 litres, so the 100ml bottle (£38.95) makes over 3,000 litres of feed. Already on CANNA? CANNA Silica (£19.99) slots straight in, as long as you're not running PK 13/14 with it. Watching the pennies? Shogun Silicon starts at £4.95. And if you foliar spray, Mills Vitalize leaves no residue on the leaves. Whichever you pick, most silica goes in the tank first. More on that below.
The best silica supplements
Grow Genius Mono Silicic Acid
Mono silicic acid, made in the UK, and the dose is daft. 0.3ml per 10 litres. That's not a typo. Even the little 10ml bottle makes 333 litres of feed.
- 40% mono silicic acid
- pH neutral
- Soil, coco and hydro
- Feed or foliar
- Doesn't touch your pH, so it can go in before or after the nutrients. One less thing to get in the wrong order
- Works as a foliar spray on its own (0.5ml per litre, once a fortnight) if you can't get it into the feed
- Stable until it meets water. Grow Genius just suggest using it within three years so the bottle stays sound
Mills Vitalize
Mills' own patented, stabilised silicic acid. And the reason most people buy it is the spray bottle. It leaves zero residue on the leaves, which is more than you can say for a lot of foliar products.
- Stabilised silicic acid
- 0.2ml per litre
- Root drench or foliar
- Soil, coco and hydro
- Drops to 0.1ml per litre in the last stretch of bloom, so a 250ml bottle goes further than you'd think
- Made to run alongside Mills Basis A&B in the tank, but happy as a standalone spray too
CANNA Silica
CANNA's newer silica, a 2-in-1 of colloidal and nano silicon. Built to slot into a CANNA programme like CANNA Coco A&B or Aqua Vega without any head scratching.
- Nano and colloidal silicon
- 1 to 2ml per litre
- Adds potassium too
- All media
- Gives a bit of potassium alongside the silicon
- CANNA pitch it for helping plants cope with heat, drought and the odd cold snap. Handy in a loft
Dutch Pro Silica (Von Liebig)
Highly concentrated silicon dioxide, using what Dutch Pro call a nanotechnology formula. 0.4ml per litre from the start of veg to the end of flower.
- Silicon dioxide
- 0.4ml per litre
- All irrigation systems
- Hydro, coco and soil
- One dose the whole way through. No chart to squint at
- Pairs with Dutch Pro Keep It Clean, Multi Total and Leaf Green if you're running the rest of the range
Plagron Silic Rock
Plagron's silicon for soil and coco growers. 1ml per litre at every watering, start to finish. That's the whole instruction sheet, more or less.
- 1ml per litre
- Every watering
- Soil and coco
- Up to 20L
- The 1:1000 dose is easy to measure with a normal measuring cylinder, no pipette needed
- Shake, add, stir, water as normal
Shogun Silicon
The cheap one, and nothing wrong with that. 1ml per litre at every feed, and the 5L is £29.95. Works out about 60p per 100 litres of feed.
- 1ml per litre
- Every feed, veg and flower
- Soil, coco and hydro
- 250ml to 25L
- Sizes from a 250ml tester to a 25L drum, so it grows with you
- Shogun pitch it as a help against botrytis too
Shop all silica and silicon supplements
Getting silica into the tank
This is where people come unstuck. Not which bottle. The order.
A lot of liquid silicon is potassium silicate, and it pushes your pH up. Pour it into a tank that's already full of nutrients and it can react and drop out of solution. Then you've paid for silica that's sat on the bottom of the tank doing nothing.
- Start with plain water. Nothing else in the tank yet.
- Silica goes in first. Shake the bottle, measure it out, give it a good stir.
- Check the pH. CANNA say bring it to around 7 at this point, Shogun say get it below 7.
- Now add your base nutrients and the rest of your additives, as per their labels.
- Final pH check. Bring it down to your target. CANNA quote 5.2 to 6.2 for hydro and coco.
The odd one out is Grow Genius Mono Silicic Acid. It's pH neutral, so Grow Genius say add it before or after the nutrients, whatever suits you. BAC Silica Power is a first-in job like the others.
And you'll be checking pH twice, so a decent pen helps. Our pH and EC meter guide has the ones we'd buy.
At a glance
Bottle prices don't tell you much on their own, because the doses are all over the place. So we've worked out roughly what each one costs per 100 litres of feed.
| Supplement | Dose | Per 100L of feed | Price |
|---|---|---|---|
 Grow Genius Mono |
0.3ml per 10L | About £1.17 (100ml) | From £20.95 |
 Mills Vitalize |
0.2ml per L | About £3.32 (1L) | From £53.99 |
 CANNA Silica |
1 to 2ml per L | £2.00 to £4.00 (1L) | £19.99 |
 Dutch Pro Silica |
0.4ml per L | About £3.12 (1L) | From £33.00 |
 Plagron Silic Rock |
1ml per L | About £1.40 (1L) | From £13.99 |
 Shogun Silicon |
1ml per L | About £0.90 (1L) | From £4.95 |
Prices as at November 2026. Cost per 100L is worked out from the label dose and the bottle size in brackets, using the higher dose where Mills give two. Check the product page for the live price.
How to choose
- Want one that just works in anything? Grow Genius Mono Silicic Acid. pH neutral, tiny dose, and the mixing order stops mattering.
- Already on CANNA? CANNA Silica. Just leave the PK 13/14 on the shelf while you're using it.
- Running Mills or Dutch Pro? Stick with the house silica, Mills Vitalize or Dutch Pro Silica. Same goes for BAC growers with BAC Silica Power (from £27.00).
- Hand watering soil or coco? Plagron Silic Rock. Keep it out of DWC and NFT though.
- Watching the pennies? Shogun Silicon, or Growth Technology Liquid Silicon at £7.49 a litre.
- Whatever you buy, read the mixing bit above before it goes anywhere near your tank.
Getting new roots going as well? Our root stimulator guide covers that end of things.
Quick answers
Do I need a silica supplement for my plants?
It's not a must, but it's one of the cheaper additives going. The makers all pitch it for much the same thing: stronger cell walls, sturdier stems and plants that cope better with heat and stress. Plagron describe it as fixing a hidden silicon deficiency.
What's the difference between mono silicic acid and liquid silicon?
Mono silicic acid is the form plants can use straight away. Standard liquid silicon is usually potassium silicate, which the plant has to break down first. Grow Genius say that's why their mono still works when you only use it as a foliar spray.
When should I add silica to my nutrient tank?
First, into plain water, before any other nutrients. Check the pH, then add your base feeds and adjust the pH again. Grow Genius Mono Silicic Acid is the exception. It's pH neutral, so it can go in before or after.
Does silica raise pH?
Many do. Shogun describe their silicon as a natural pH up, and CANNA tell you to bring the tank to around pH 7 after adding CANNA Silica, before the base nutrients go in. Grow Genius Mono Silicic Acid is pH neutral.
Can I use silica with PK 13/14?
Not with CANNA Silica. CANNA advise against it, because CANNA Silica contains potassium and the two together can cause lockout and leaf burn. With other brands, check the label first.
Can I use silica in DWC or recirculating hydro?
Yes, with most of them. Grow Genius, CANNA, Dutch Pro and Shogun all list hydro. Plagron Silic Rock is the one to avoid, as Plagron don't recommend it for NFT, DWC or aeroponics.
Still stuck? Give us a ring on 020 8686 9643 or email info@thehydrobros.com.
Or pop into the shop for a natter: Unit 12, Progress Business Park, Progress Way, Croydon CR0 4XD.
More grow guides
- Best root stimulators
- Best coco coir and coco mixes
- CANNA Coco A&B: a closer look
- Best pH and EC meters
- Mastering EC: feed strength in hydroponics
- How to read NPK ratios
The Hydro Bros Team. We sell this kit and talk growers through it every day in our Croydon shop.
