Short version? Rock Resinator is a flower enhancer for growers who want one bloom additive running from week 2 of flower right up to the chop, rather than a quick shot of PK near the end. From £25.00 for the 250ml. It goes in soil, coco or hydro. There's no kit with it, but the bigger bottles get cheaper quickly: the 1L is £46.05 less than four 250mls.
Rock Resinator
- Flower enhancer
- Phosphorus, potassium and amino acids
- 1 to 3.5ml/L
- Week 2 of flower to harvest
- Soil, coco and hydro
- 250ml to 20L
The numbers
| What it is | A flower enhancer you add to your base feed in bloom |
| What's in it | Soluble potash, potassium, organic acids and amino acids, in a phosphorus and potassium blend |
| Standard dose | 1 to 2ml per litre |
| Late flower dose | Building up to around 3 to 3.5ml per litre through the final weeks |
| When to use | From the start of week 2 of flower, once flower sites are forming, through to harvest. That includes the flush period |
| Grow media | All media and systems: soil, coco and hydro |
| Sizes | 250ml, 1L, 5L, 10L, 20L |
| Price | £25.00 (250ml) up to £665.00 (20L) |
Rock Resinator FAQs
Is Rock Resinator any good?
For the right grower, yes. It's a long-run bloom additive with phosphorus, potassium, organic acids and amino acids, and you use it from week 2 of flower right through to harvest in any medium. It costs more per bottle than a basic PK shot, though, so it suits someone who wants one booster doing the whole of bloom.
Rock Resinator or Advanced Nutrients Big Bud?
Both feed extra phosphorus, potassium and amino acids in flower. Big Bud is cheaper per bottle and is used in the earlier part of bloom, roughly weeks 2 to 4, with Overdrive taking over at the end. Rock Resinator runs from week 2 to harvest on its own. If you're already on an Advanced Nutrients base, Big Bud fits. If you want one bottle for the whole of bloom, go Resinator.
How much Rock Resinator do I use per litre?
1 to 2ml per litre as standard, building up to around 3 to 3.5ml per litre through the final weeks. That's 10 to 20ml in a 10 litre can to start with.
When should I start using Rock Resinator?
At the start of week 2 of flowering, once you can clearly see flower sites forming. Then keep it going until harvest.
Can I use Rock Resinator during the flush?
Yes. The feeding directions say to keep using it through the flush period, at the higher 3 to 3.5ml per litre rate. If you flush with plain water only, that's your call, but it's not how the bottle is meant to be used.
Does Rock Resinator work in coco and hydro?
Yes. It's made for all growing media and systems, so soil, coco and hydro are all fine.
What is in Rock Resinator?
Soluble potash, potassium, organic acids and amino acids, in a blend built around phosphorus and potassium. The product description doesn't give an NPK figure.
Which size of Rock Resinator should I buy?
The 250ml is fine for a small tent or a first try. Most people running it every feed will save by going to the 1L, which works out £46.05 cheaper than four 250ml bottles.
What it does well
It covers the whole of bloom. Lots of PK products are a short, sharp hit you add for a few days near the end and then forget about. Resinator goes in from week 2 and stays in. One bottle, one habit.
And it's not just raw phosphorus and potassium. Rock put organic acids and amino acids in there too, aimed at the flowering sites. Their pitch is more essential oil and more flower mass. We can't promise you a figure on the scales and we won't pretend to. But that's what it's built for.
It also doesn't care what you grow in. Soil, coco, hydro. Same bottle.
- One additive from week 2 of flower to harvest
- Phosphorus and potassium plus organic acids and amino acids
- Works in soil, coco and hydro
- Five sizes, from a 250ml to try it up to a 20L for big rooms
Where it falls short
Good fit if you...
- want one bloom additive for the whole of flower
- grow in soil, coco or hydro and don't fancy juggling boosters
- are happy to pay a bit more for a blend with amino and organic acids
Look elsewhere if you...
- just want a cheap PK shot for the last few weeks
- are watching the pennies on a big room
- like to see an NPK figure on the label before you buy
Which version to buy
Same stuff in every bottle. It's just about how much you get through, and we've checked each size against buying the smaller one several times over.
| Size | Price | Saving |
|---|---|---|
| Rock Resinator 250ml | £25.00 | n/a |
| Rock Resinator 1L | £53.95 | £46.05 vs four 250ml |
| Rock Resinator 5L | £179.95 | £89.80 vs five 1L |
| Rock Resinator 10L | £342.00 | £17.90 vs two 5L |
| Rock Resinator 20L | £665.00 | £19.00 vs two 10L |
Prices as at November 2026.
The big jump is from 250ml to 1L. Running it at 2ml per litre, a 250ml bottle covers 125 litres of feed, which goes faster than you'd think in a decent tent. Past the 5L the savings flatten out, so only go bigger if you've got the room to get through it.
How to use it
- Wait for the start of week 2 of flower, when the flower sites are clearly forming.
- Mix up your usual base feed in the can or tank.
- Add Rock Resinator at 1 to 2ml per litre and give it a stir.
- Check your pH and EC before you feed.
- As you head into the last weeks, build the dose up to around 3 to 3.5ml per litre.
- Keep it in right through to harvest, flush period included.
Looking after it
It's a bottle of feed, so there's not a lot to it. A few habits help, mind.
- Keep it cool and dark. Out of the tent and off the windowsill, with the cap done up.
- Measure it properly. At 1 to 3.5ml per litre, guessing with a glug from the bottle is how feeds go wrong.
- Watch your EC as the dose climbs. Going up to 3.5ml per litre adds strength to the feed, so check it with a meter rather than hoping.
- Keep your pH pen calibrated. Additives shift pH a touch, and a pen that's drifted won't tell you.
Not sure which meter suits you? Our best pH and EC meters guide goes through the lot.
How it stacks up
| Bloom additive | When it's used | 250ml | 1L |
|---|---|---|---|
| Rock Resinator | Week 2 of flower to harvest | £25.00 | £53.95 |
| Advanced Nutrients Big Bud | Earlier bloom, roughly weeks 2 to 4 | £11.80 | £28.50 |
| Advanced Nutrients Overdrive | Last 3 weeks of flower | £10.79 | £30.50 |
| CANNA PK 13/14 | One 3 to 6 day shot, about 3 weeks before harvest | £5.50 | £15.00 |
| CANNA Boost Accelerator | From flowers forming to finish | £21.50 | £53.99 |
Prices as at November 2026. Big Bud and Overdrive are designed to be used one after the other, so budget for both.
Price-wise, Resinator sits right next to CANNA Boost, which also runs most of bloom. The Advanced Nutrients pair costs less per bottle but you'll need two of them. And PK 13/14 is the cheap and cheerful option if a short end-of-grow boost is all you want.
Got a question about it? Give us a ring on 020 8686 9643 or email info@thehydrobros.com.
Or pop into the shop and have a look at one: Unit 12, Progress Business Park, Progress Way, Croydon CR0 4XD.
More grow guides
- Best silica supplements for growers
- Best root stimulators for growers
- CANNA Coco A&B closer look
- Bluelab Truncheon closer look
- How to read NPK ratios
- Mastering EC: feed strength made simple
The Hydro Bros Team. We sell this kit and talk growers through it every day in our Croydon shop.
