Grotek Final Flush - Nutrient Salt Flush for Cleaner-Tasting Harvests
Best for: growers finishing a crop in soil, coco or hydro who want to strip out built-up fertiliser salts before harvest.
Our thoughts
This is a pre-harvest essential rather than a nice-to-have — feed heavy for weeks and your medium ends up holding onto salts that plain water alone won't shift. Final Flush is built specifically to grab hold of that leftover fertiliser and get it out, which is the difference between a clean finish and a harsh, chemical aftertaste. It's a straightforward job: dose it, run it through, done.
Grotek Final Flush is a flushing agent — not a fertiliser — designed to remove excess nutrient salts that build up in growing media and hydro systems after weeks of regular feeding. It carries an NPK of 0-0-0, because its job isn't to feed the plant at all; it's to solubilise and strip out the fertiliser residue that's bound to the substrate or dissolved in the reservoir, correcting over-feeding issues and reducing the risk of salt-related nutrient lockout.
Plain water flushing only carries away nutrients that are already dissolved in solution — it can't touch the salts that have bonded to soil, coco or rockwool particles. Final Flush's solubilising compounds are formulated to loosen and lift that bound residue as well, which is the whole point of using a dedicated flush rather than just running extra water through.
How it compares
Final Flush sits alongside the handful of established flushing concentrates used at the end of a feed cycle.
- Vs General Hydroponics FloraKleen: FloraKleen is one of the most widely used flush concentrates and works on a similar principle — Final Flush competes closely on price and performance in the same "concentrated flush" category.
- Vs House & Garden's flush and root-zone products: House & Garden's range leans more towards multi-purpose root conditioning alongside flushing, whereas Final Flush is a more single-purpose, dedicated salt-stripping product.
- Vs flushing with plain water only: water-only flushing is free but slower and less thorough, since it can't shift salts already bound to the growing medium — a dedicated flush like this does that job properly in a fraction of the time.
If your priority is a clean, salt-free finish without guessing how many litres of plain water is "enough," a dedicated flush like this earns its place in the last week of the grow.
Usage guidance
Shake well before use and watch for the tell-tale sign you need it: a white, powdery salt residue on the surface of your growing medium.
Dosage
Use 10ml of Final Flush per 5 litres of water (roughly 2 teaspoons per 5 litres).
Hydroponic systems
Add the mixed solution to your reservoir in place of nutrient solution and run the system for around one hour.
Soil and soilless (coco, rockwool)
Apply the mixture liberally to the top of the container and let the excess drain out the bottom. Repeat once more if salt build-up is heavy, then wait a week before resuming your regular feed.
Pre-harvest
Run it 7-10 days before harvest to clear residual fertiliser salts and flavours ahead of cutting down.
Technical specifications
- NPK: 0-0-0 (flushing agent, not a fertiliser)
- Format: Liquid concentrate
- Dosage: 10ml per 5 litres of water
- Use case: Salt/nutrient lockout correction and pre-harvest flush
- Compatible media: Soil, coco, rockwool and recirculating hydroponic systems
- Timing: During the grow if salt build-up appears, or 7-10 days pre-harvest
- Manufacturer: Grotek
- Bottle size (this listing): 1 litre
- Range: Also available in flavoured variants (e.g. Strawberry, Grapefruit) from the same manufacturer, aimed at finishing taste as well as salt removal
Who this is for
- Growers who've been feeding heavily and are seeing white salt crust on the medium surface
- Anyone finishing a coco or hydro crop who wants a clean, chemical-free-tasting harvest
- Soil growers dealing with nutrient lockout who need to reset before going back on a feed schedule
Best used as a planned last step before harvest, not just as an emergency fix once a plant's already showing lockout stress.
Our take
Final Flush does one job and does it properly — strip out the fertiliser your plant doesn't need anymore so what you harvest tastes and burns the way it should. It's cheap insurance against weeks of careful feeding being undone by a harsh, salty finish.
One we sell a lot of for growers heading into their last week before chop — worth having in the cupboard before you need it.
