Short version? For most soil growers, BioBizz Bio-Grow and BioBizz Bio-Bloom are where to start. They're from £4.50 a bottle, and the BioBizz Indoor Try-Pack gets you both plus Top-Max for £13.50, which is £3.59 less than buying them separately. Can't be doing with feed days? Bio Tabs Guerrilla Tabs go in the pot and release slowly. Reviving tired soil, BioBizz Fish-Mix is the one, if you can live with the whiff. And if you fancy a full organic range from someone else, Crazy Hills Organic Upthrive and Prosper sort veg and flower.
The best organic nutrients for soil
BioBizz Bio-Grow
The organic grow feed most soil growers start on. It's made from Dutch sugar beet extract with kelp, humic acids and 70 trace elements, and it works by waking up the bacteria in your soil rather than force feeding the plant.
- NPK 4-3-6
- 2 to 4ml per litre
- Every watering
- 250ml to 20L
- Start once the first true leaves show, then use it at every watering
- Heaviest use is in veg, but it can run right through the grow
- Growing in BioBizz All-Mix? Drop to 1ml per litre, because that soil's already fed
BioBizz Bio-Bloom
Bio-Grow's flowering partner. NPK with natural enzymes and amino acids, so it feeds the plant and the microbes at the same time. It's certified under EU Organic Input, NOP, Ecocert and Clean Green, if the paperwork matters to you.
- 2 to 4ml per litre in soil
- First flowers to harvest
- Soil, coco, hydro
- 250ml to 20L
- Swap it in at the first signs of flowering and use it every watering through to harvest
- In coco or hydro, drop to 1 to 3ml per litre and go by your EC
- BioBizz suggest adding Top-Max from mid flower
BioBizz Fish-Mix
One of the original organic feeds out of the Netherlands, and still one of the most popular. North Sea fish emulsion plus sugar beet extract. It's great at building up the microbial life in old or knackered soil.
- NPK 5-1-4
- 1 to 4ml per litre
- Drench or foliar
- 250ml to 20L
- Use it from seedling stage through veg, and into flower if you want to keep the leaves green
- Works as a foliar spray too, at 1 to 2ml per litre
- Good for "fattening up" soil you're reusing
Bio Tabs Guerrilla Tabs
Slow release organic tablets. Push them into the pot, water them in, and they feed the plant and condition the soil over time. Made for big containers and anyone who forgets what day it is.
- NPK 15-7-8
- 10g tablets
- 4 per 10L pot
- 20 or 200 tabs
- 4 tabs per 10L pot, 6 per 20L, 8 per 30L. In the ground it's 4 per plant
- Push them 5cm below the surface and water in
- Control Union certified 100% organic ingredients
Crazy Hills Organic Upthrive
Crazy Hills do a whole organic line, and Upthrive is the grow feed. NPK 4-1-5 with micronutrients, vitamins, betaines and sugars that feed the microbes round the roots. Crazy Hills Organic Prosper (NPK 2-3-3, from £12.55) takes over for flower.
- NPK 4-1-5
- Veg stage
- Pairs with Prosper
- 1L, 5L, 10L
- Simple two bottle routine. Upthrive in veg, Prosper once you flip
- Prosper bumps up phosphorus and potassium for buds, flowers and fruit
- There's a booster, Élan, and a flowering stimulant, Spark, if you want the full set
Shop all organic plant nutrients
Feeding organic in soil without overdoing it
Organic feeds don't work quite like bottled minerals. Most of them feed the life in your soil, and the soil life feeds the plant. Bit slower. Much more forgiving.
But you can still overdo it, especially in a soil that's already got food in it.
- Check what's in your soil first. A pre-fertilised mix like BioBizz All-Mix needs far less on top. BioBizz drop Bio-Grow to 1ml per litre in All-Mix for exactly that reason.
- Pick one veg feed. Bio-Grow, Fish-Mix and Upthrive are all doing the veg job. You don't need two of them at full whack.
- Swap feeds when the plant changes stage. Grow feed in veg, bloom feed from the first flowers. Simple, and it's what all three ranges here are built around.
- Start low. Most of these give a range, so begin at the bottom and work up if the plant's asking for more.
- Measure after mixing. Our pH and EC meters guide covers the kit.
Still weighing up organic against mineral? We've written about organic vs mineral nutrients and what we see in the shop.
At a glance
What each one does and when it goes in.
| Feed | Type | When | Price |
|---|---|---|---|
 BioBizz Bio-Grow |
Liquid grow feed, 4-3-6 | First true leaves, mainly veg | From £4.50 |
 BioBizz Bio-Bloom |
Liquid bloom feed | First flowers to harvest | From £4.50 |
 BioBizz Fish-Mix |
Fish emulsion, 5-1-4 | Seedling to veg, into flower | From £4.49 |
 Bio Tabs Guerrilla Tabs |
Slow release tablet, 15-7-8 | In the pot, feeds over time | From £14.00 |
 Crazy Hills Organic Upthrive |
Liquid grow feed, 4-1-5 | Veg | From £10.75 |
 Crazy Hills Organic Prosper |
Liquid bloom feed, 2-3-3 | Flower | From £12.55 |
Prices as at November 2026. Check the product page for the live price.
How to choose
- First organic grow? BioBizz Bio-Grow and Bio-Bloom. The Indoor Try-Pack is the cheap way to have a go.
- Forgetful, or growing in big pots? Bio Tabs Guerrilla Tabs, with Guerrilla Juice once a week from week four.
- Reusing old soil? BioBizz Fish-Mix to get the life back into it. Have the carbon filter running.
- Want a full line-up from one brand? Crazy Hills Upthrive and Prosper, or the Full Range 1L Kit if you want the extras too.
- Whichever you go for, read the overdoing it bit above first.
Planning the flowering stretch? Our bloom boosters guide covers organic options like BioBizz Top-Max.
Quick answers
What is the best organic nutrient for soil?
For most growers, BioBizz Bio-Grow for veg and BioBizz Bio-Bloom for flower. They're from £4.50 a bottle, used at every watering, and the BioBizz Indoor Try-Pack gets you both plus Top-Max for £13.50.
Is BioBizz organic?
Yes. BioBizz Bio-Bloom is certified under EU Organic Input, NOP, Ecocert and Clean Green, and Bio-Grow is made from organic Dutch sugar beet extract with kelp and humic acids.
How much BioBizz Bio-Grow per litre?
2 to 4ml per litre at every watering, starting once the first true leaves show. In BioBizz All-Mix soil, drop it to 1ml per litre.
Can I use organic nutrients in pre-fertilised soil?
Yes, but go lighter. A pre-fertilised mix already has food in it, which is why BioBizz cut Bio-Grow to 1ml per litre in All-Mix. Start low and build up only if the plant needs it.
How many Guerrilla Tabs per pot?
4 tabs per 10 litre pot, 6 per 20 litre and 8 per 30 litre. For plants in the ground it's 4 per plant. Push them 5cm below the surface and water in.
Does BioBizz Fish-Mix smell?
Yes, it's made from fish so it's pretty fishy in the bottle. The smell drops off once it's diluted, but indoors you'll want good ventilation and odour control.
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
- Organic vs mineral nutrients
- Best bloom boosters
- Best CalMag supplements
- Best root stimulators
- Best fabric pots
- Best pH and EC meters
The Hydro Bros Team. We sell this kit and talk growers through it every day in our Croydon shop.
