First steps
Start here
- Scrape off fish residue and slime right away, and don't rub it in.
- Rinse with cool or lukewarm water, not hot.
- Test any cleaner on a hidden spot first.
- Don't let any cleaner or soap dry on the deck.
Fish residue on a deck is slime and oil that work into the grain, and they carry the same fishy odor you'd find on clothing. Fresh residue comes up with cool water and mild dish detergent, so try that before anything stronger. Weathered decks need extra caution: if the wood has gone fully silver, those fibers should stay in place, and a pressure washer can damage boards when used carelessly.
If you're after a dock cleaner that's safe for fish, keep the strongest products off the boards that touch the water. Once the slime is lifted, an odor eliminator or oxygen bleach powder is the kind of product to reach for. If the smell hangs on after two rounds, that's the point to call a deck cleaning pro rather than keep going.
Before you start
What decks & wood fences can take
Safe to use2
- Water
- Oxygen bleach
Use with care5
- Soaking
- Chlorine bleach
- Solvents (alcohol, spot removers)
- Acids (vinegar, lemon)
- Scrubbing and abrasives
6 items
What you'll need
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- Garden hoseRinses the boards and wets the spot before and after each cleaning step.
- Plastic scraper or paper towelsLifts residue off the wood without pushing it into the grain. (opens Amazon)
- Mild dish detergentMakes the water-and-soap scrub that handles the residue. (opens Amazon)
- Stiff synthetic-bristle brushScrubs along the grain, the direction the wood needs. (opens Amazon)
- Oxygen-bleach deck cleanerFor mildew or organic growth, applied in sections with a label dwell time. (opens Amazon)
- Plastic drop clothProtects nearby plants from overspray. (opens Amazon)
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6 steps
Step by step
Step 1 of 6
Scrape off the fish residue
Scrape or blot the fish residue and slime off right away, lifting it away from the boards. Use a plastic scraper or paper towels, and work before the residue dries on the wood.
Careful. Don't rub or brush the residue; that pushes the slime deeper into the grain.
Step 2 of 6
Test, then rinse with cool water
Before any cleaner goes on the deck, test it on a hidden spot. Then rinse the area with a garden hose, or sponge it with cool or lukewarm water.
Careful. Hot water can set the stain, so keep the rinse cool or lukewarm.
Step 3 of 6
Scrub with mild dish detergent
Mix mild dish detergent into a bucket of water and work it into the boards with a stiff synthetic-bristle brush. Brush along the grain, one section at a time.
Step 4 of 6
Check for mildew after scrubbing
If black spots are still there after the soap scrub, they may be mildew or organic growth. That's the point to switch to the oxygen-bleach cleaner rather than adding more soap.
Step 5 of 6About 15 minutes
Apply the oxygen-bleach deck cleaner
Apply the oxygen-bleach deck cleaner to one section at a time, following the label. Keep it wet for the label's dwell time, about 15 minutes, and mist the section with the hose if it starts to dry.
Tip. Sweep away leaves and debris first, and protect nearby plants with a plastic drop cloth, spraying them with water to dilute overspray.
Careful. Never let the cleaner or soap dry on the deck.
Step 6 of 6
Scrub along the grain and rinse
Scrub the treated section along the grain with the stiff brush, then rinse it thoroughly with the hose before moving on. Check that no cleaner or soap is left on the boards when you finish.
If you'd rather buy than mix
Best products for fish smell on decks & wood fences
Choose an oxygen-bleach deck cleaner made for wood and follow its label for dwell time. Pair it with a stiff synthetic-bristle brush rather than a wire one.
OxiClean Versatile Stain Remover Powder
How we picked these: each product is made for this type of stain, its maker doesn't warn against using it on decks & wood fences, and its directions fit the steps above.
Finished the steps? How does it look?
Nice work. Let it dry completely and check it again in good light. Here is what done looks like:
How to tell it's really gone →A faint mark usually needs one more round, not a stronger product.
A smell that keeps coming back needs the longer treatment.
If the smell lingers →When to call a professional →How to tell it's working
Once the deck is dry, the smell and the stain should both be gone. If either is still there, repeat the soap scrub and rinse before moving to the oxygen-bleach cleaner for any growth.
What changes for yours
Adjust for your decks & wood fences
Pressure-treated deck
Pressure-treated wood is where chlorine bleach is off the table: it breaks down the lignin in the wood, corrodes metal fasteners, harms plants and doesn't kill mildew spores. Use the oxygen-bleach deck cleaner for any mildew instead.
The soap wash and hose rinse stay the same, so start there and only move to the oxygen cleaner if spots remain.
Older CCA-treated deck
Decks built with older arsenic-treated lumber, known as CCA, need extra care. Wetting the wood raises the arsenic at its surface, so keep kids and pets off the wet boards and off them until they're fully dry.
Don't cut or burn old boards, since sawdust and smoke contain arsenic. Replacing old CCA lumber is the safer long-term fix.
Western redcedar and other soft woods
Soft woods like western redcedar need a lighter touch. Don't scrub aggressively with caustic cleaners, and don't power wash them, since either one removes wood from the surface.
Keep to the same hose rinse and brush along the grain, and use the oxygen-bleach deck cleaner only if you see mildew. Let the wood dry fully before deciding on another round.
Tannin bleed or rust streaks
Reddish-brown streaks come from tannin bleed or rust from nails, and they need a different product than the soap wash. Use an oxalic-acid wood brightener per its label on those streaks.
Rinse all oxygen cleaner off first, because the acid neutralizes oxygen cleaners. Keep the brightener for the streaks only, not the whole deck.
If the smell lingers
Old stain or sealer is the stubborn case, and it's a different job from fish residue. Weathered, grayed decks can be restored with a commercial deck cleaner, brightener or restorer, which takes off mildew and dirt so the wood's own color shows.
If the stain has dried into the wood, the cleaner alone may not get it all out. Old finish comes off with a stain and sealer remover, which you neutralize with a brightener and then lightly sand once the wood is dry.
If the natural color has leached out, the wood will stay silver when dry, and those fibers should be left in place rather than scrubbed harder. Expect a restored deck to look cleaner and brighter, not like new wood.
Vinegar, baking soda, peroxide and more
Do home remedies work on fish smell on decks & wood fences?
You'll see plenty of home remedies for fish smell, so here's where each one fits on a deck. Two make it into the steps, and the rest either don't suit wood or belong to fabric.
Works2Skip4
What makes it worse
Mistakes to avoid
Don't use a tornado pressure-washer tip
Rotating tornado tips and narrow streams are not for decks. If you pressure wash at all, use a fan tip at the lowest pressure that cleans, and spray with the grain.
Don't use steel wool or wire brushes
Leftover iron in them reacts with the wood's natural extractives and stains the boards. A stiff synthetic-bristle brush along the grain does the scrubbing without that risk.
When to call a professional
A deck can be damaged in the wrong hands, so if you're unsure about pressure washing or restoring old finish, hire a professional. For a stubborn stain on old wood, that's the right call before you try anything harsh.
Questions
What dock cleaner is safe for fish?
Look for a fish-safe rating on any cleaner's label before you buy it, and if the label doesn't give one, keep the cleaning on the boards. Use the mild dish detergent wash first, reach for the oxygen-bleach deck cleaner only for mildew, and rinse everything off with the hose.
Will the fish smell come out of the wood?
Usually, once the residue and slime are gone. If the smell lingers after a full soap wash and rinse, the residue is likely still in the grain, so scrub that section again before moving to the oxygen cleaner.
What if the spots look black?
Black spots may be mildew or organic growth, which is when the oxygen-bleach deck cleaner earns its place. If they don't lift after that, the wood may be too weathered for a full clean, and the restoring options below are the next step.
Can I pressure wash the deck to clear the residue?
You can, if you keep the pressure low and use a fan tip, spraying with the grain. Test a hidden spot first, and stop if it starts to damage the wood.
Is vinegar a good option for a fish-smelling deck?
No need for vinegar on a deck: the mild dish detergent wash handles the residue. The mild dish detergent wash handles the residue, and the oxygen-bleach deck cleaner handles mildew.
Should I rinse before I scrub?
Yes. Rinse with cool or lukewarm water first, so you can see exactly what residue is left to scrub. A rinse loosens the loose slime, which makes the soap wash that follows far more effective on what remains.
Fish Smell on other materials
Other stains on decks & wood fences
Start from the bigger picture
How we know this
Every method, amount and warning here comes from university extension services, industry bodies and product makers. We read them, check every step for unsafe combinations and changed amounts, and write it up so you can follow it.