This Biobizz Fish-Mix nutrient guide is your complete resource for indoor growing success. April 2026 | Reading time: approx. 7 minutes
How to use Biobizz Fish-Mix organic nutrient as a root drench and foliar feed during vegetative growth.
- Determine the correct dose from the Biobizz chart
Consult the Biobizz Fish-Mix dosage chart for your grow stage. The typical dose is 1–4ml per litre, increasing gradually through the vegetative phase. Start low and build up as plants develop to avoid over-stimulation.
- Mix into lukewarm water and stir thoroughly
Add Fish-Mix to lukewarm water and stir well before adding other nutrients. The product has a strong smell — this is normal and indicates the organic compounds are active. Mix in a well-ventilated space.
- Apply as a root drench during vegetative growth
Water the root zone with your Fish-Mix solution as normal. It delivers nitrogen and stimulates microbial activity in the growing medium throughout the veg phase. Taper the dose off as plants enter early flowering.
- Optional: apply as a foliar spray in early veg
Dilute to 1ml per litre and spray leaves directly for accelerated vegetative growth. Apply in the evening or with lights dimmed to avoid scorch. Do not foliar spray once flowering begins.
- Flush with plain water in the final two weeks
In the final one to two weeks before harvest, flush with plain pH-adjusted water to clear residual nutrient salts — standard practice with organic nutrients to ensure clean, full-flavoured results.
What Is Biobizz Fish-Mix?
Biobizz Fish-Mix is one of those products that has been quietly doing its job in grow rooms and gardens around the world for decades. It’s not a gimmick. It’s not new. It has an NPK of 5-1-4, it smells extraordinary, and growers keep using it because it works consistently.
At its most basic, Fish-Mix is a cold-pressed emulsion made from North Sea fish, blended with Dutch sugar beet extract. The fish provides a dense, fast-acting nitrogen hit alongside a rich profile of organic proteins, amino acids, and lipids. The sugar beet extract adds a readily available carbon source that acts as fuel for the beneficial bacteria and fungi living in your growing medium. Together, they don’t just feed the plant — they condition the entire root zone.
It’s certified OMRI Listed and approved by Control Union, confirming it’s free from chemical acids and synthetic preservatives. Whether you’re running a fully organic programme or a synthetic regime that you want to add some biological activity to, Fish-Mix fits without disrupting your base nutrients.
The NPK: What 5-1-4 Actually Means in Practice
The 5-1-4 NPK breakdown is the starting point for understanding when and how to use Fish-Mix effectively.
- Nitrogen (5): The headline number. Fish-Mix is the strongest nitrogen source in the Biobizz range. This drives rapid vegetative growth — leaf size, node spacing, stem strength. In rich substrates like All-Mix, which already contains significant nitrogen, you apply Fish-Mix sparingly and let the substrate do some of the work. In light or inert media, you lean on it more heavily.
- Phosphorus (1): Low, as you’d expect for a vegetative product. Phosphorus becomes important in the transition to flower and peak bloom — that’s Bio-Bloom’s job, not Fish-Mix’s.
- Potassium (4): Solid supporting role. Potassium regulates water movement through the plant, strengthens cell walls, and supports overall plant health. The 4 here makes Fish-Mix more balanced than the nitrogen-heavy headline suggests.
The practical upshot: Fish-Mix is a veg-phase product. Its nitrogen profile makes it an excellent substitute for Bio-Grow during vegetative growth, particularly in outdoor and living soil applications where the smell is less of an issue.
Fish-Mix vs Bio-Grow: The Decision Most Growers Get Wrong
This is the most common source of confusion in the Biobizz range, and it’s worth addressing directly. Fish-Mix and Bio-Grow are not meant to be used together — both are high-nitrogen products, and combining them creates a real risk of nitrogen toxicity even in rich substrates.
| Factor | Fish-Mix | Bio-Grow |
|---|---|---|
| NPK ratio | 5-1-4 | 4-3-3 |
| Primary role | Vegetative growth + soil conditioning | Vegetative growth (lighter, balanced) |
| pH impact | Drops to ~6.2–6.3 | Self-regulates to ~6.5 |
| Smell | Very strong (North Sea fish) | Mild, less pungent |
| Best for | Outdoor grows, living soil, heavy-feeding veg | Indoor, smell-sensitive grows |
| Use in flower? | Early flower only — stop 2 weeks before flip | Can run through to late flower |
| Use together? | No — both high in N, do not combine | |
| Foliar feed? | Yes — 1–2 ml/L in veg only | Yes — same rate |
| OMRI certified? | Yes | Yes |
The practical rule most experienced Biobizz growers follow: use Fish-Mix for the vegetative phase, switch to Bio-Grow two weeks before flipping to flower (to let nitrogen levels settle), then move to Bio-Bloom through the flowering period. If you’re growing outdoors where smell is a non-issue, Fish-Mix can run all the way through early flower because it accelerates microbial soil activity so effectively in living soil conditions.
Biobizz Fish-Mix Dosage Guide
The most important thing to understand about Fish-Mix dosing is the substrate dependency. All-Mix already contains a significant nutrient charge — you’re adding Fish-Mix on top of that. Light-Mix and Coco-Mix are leaner substrates, so you apply more. Hydro and inert media follow the same approach as coco.
| Growth Stage | Biobizz All-Mix | Light-Mix / Coco-Mix | Hydro / Inert Media |
|---|---|---|---|
| Seedlings (10–15cm) | 1 ml / litre | 1 ml / litre | 1 ml / litre |
| Vegetative Growth | 1 ml / litre | 2–4 ml / litre | 2–4 ml / litre |
| Early Flowering | 1 ml / litre | 2–4 ml / litre | 2–4 ml / litre |
| Late Flowering | Not recommended | 4 ml / litre | 4 ml / litre |
| Foliar Spray (veg) | 1–2 ml / litre | 1–2 ml / litre | 1–2 ml / litre |
Key rules: Never exceed 4 ml/litre in any substrate — Fish-Mix is highly concentrated and overdosing causes nitrogen toxicity. Shake the bottle thoroughly before every use as the emulsion separates between uses. Only mix what you plan to use immediately — once mixed with water, the organic matter begins breaking down and the smell intensifies significantly within 24 hours.
How to Apply Fish-Mix: Root Drench and Foliar Feeding
Root Drenching (Primary Method)
The standard application is as a soil drench during your regular watering routine. Shake the bottle, mix the correct dose into your water, stir, check pH, and apply to the substrate until you see slight runoff. Apply with every watering during the vegetative phase.
One important note: Fish-Mix lowers pH more than Bio-Grow does. Where Bio-Grow tends to self-regulate tap water to around 6.5, Fish-Mix typically brings the final solution down to around 6.2–6.3. This is within the optimal organic soil range, but it means you should check and adjust pH after mixing rather than assuming it’ll land where you want it.
Foliar Feeding (The Veg Growth Booster)
Fish-Mix is one of the few organic liquid fertilisers mild enough to be used as a foliar spray without burning leaves. Applied directly to foliage, it delivers an almost instant nitrogen boost that bypasses the root zone — useful for addressing early nitrogen deficiency symptoms quickly, or for maximising vegetative momentum during a fast-growth period.
Dilute to 1–2 ml per litre for foliar use. Spray 1–3 times per week during the vegetative stage. Always spray with the lights off or in the evening to prevent leaf burn. Allow 12–15 minutes for the leaves to fully absorb the solution before lights come back on.
Pro tip: Combine Fish-Mix at 1 ml/L with Biobizz Alg-A-Mic at 1 ml/L for a highly effective foliar tonic that covers nitrogen, micronutrients, and stress recovery simultaneously.
The Smell: Managing the Aroma Indoors
There’s no point dancing around it — Fish-Mix smells. It’s made from real North Sea fish, and once mixed with water and applied to warm soil under grow lights, the aroma intensifies. For indoor growers, a quality carbon filter and extraction system isn’t optional when using Fish-Mix regularly. This is one of the main practical reasons to consider Bio-Grow instead for indoor applications — the performance difference in a controlled indoor environment is relatively minor, but the smell difference is significant.
Outdoor growers tend to favour Fish-Mix precisely because they don’t have to worry about aroma — and in outdoor living soil conditions, the accelerated microbial activity it drives gives it a meaningful edge over Bio-Grow.
Watch: Dan from Biobizz Explains Fish-Mix
For a direct explanation of what Fish-Mix is, how it works, and how Biobizz recommend using it within the full range, this video from the official Biobizz DISCOVER channel is worth watching:
Frequently Asked Questions
Frequently Asked Questions
Biobizz Fish-Mix is an organic liquid fertiliser used primarily as a base nitrogen source during vegetative growth. Its 5-1-4 NPK profile delivers readily available nitrogen for leaf and stem development, stimulates beneficial microbial activity in the growing medium, and can be applied as both a root drench and an early-veg foliar spray.
Yes, though with caveats. In DWC or simpler hydro systems it works well at 2–4 ml/L. In recirculating systems, the organic particles can settle and potentially affect pumps or drippers over time — change your reservoir more frequently than you would with mineral nutrients, as the organic matter breaks down in water.
Every watering during the vegetative phase. Fish-Mix is not a once-a-week supplement — it’s a base vegetative nutrient. In coco where you may be watering daily, apply daily at the correct dose. In richer soil with less frequent watering, apply every time you water.
Biobizz advise against it. The high nitrogen content encourages vegetative responses that are counterproductive when you want the plant channelling energy into flower development and resin production. Stick to Bio-Bloom, TopMax, and Alg-A-Mic in the final weeks.
Fish-Mix is a natural product with batch variation. The colour can range from golden amber to darker brown depending on seasonal variation in the North Sea fish stock. This has no bearing on performance — Biobizz verify the NPK and biological activity of every batch through laboratory testing before it leaves the facility.
Shop Biobizz Fish-Mix at The Horticulture Company
We stock the full range of Biobizz Fish-Mix bottle sizes at The Horticulture Company, from 1 litre for home growers to larger volumes for commercial operations. One of our most consistently high-performing products and a genuine staple of the organic growing world.
Shop Biobizz Fish-Mix at The Horticulture Company →
Related Articles
- Nutrients and Additives Guide — complete hub
- The Biobizz Feeding Chart for Soil Growers
- Fish Sh!t Organic Soil Conditioner Guide
Further Reading From The Horticulture Company
For more expert growing guides, our nutrients and additives guide explains how to build an effective feed programme, while our LED grow lights comparison and grow tents guide help you optimise your growing environment. The indoor growing environment guide covers temperature, humidity and CO₂, and the complete UK grow tent guide takes you through setup from scratch.
For authoritative guidance on plant nutrition and health, the Royal Horticultural Society publishes evidence-based growing advice used by professionals and hobbyists alike. Visit The Horticulture Company’s store in Kenilworth, Warwickshire, or browse our full range of products and guides online.
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