Detritus is the fine waste that settles in your reef tank. It fuels algae and can drive nitrate and phosphate up. Good detritus control keeps water clear and coral color strong.
What detritus is and where it hides
Detritus is fish waste, uneaten food, and broken organics. It also includes sand dust and dead biofilm. It breaks down into dissolved nutrients over time. That process consumes oxygen and lowers water quality.
Most detritus settles in low-flow zones. Check behind rock stacks and under overhangs. Look in sump corners and filter sock holders. It also builds inside porous rock and thick sand beds.
Use a flashlight at night to spot it. You will see brown “snow” on the sand. You may also see cloudy puffs when a fish darts. If you can blow it off with a baster, it is detritus.
Test results can hint at hidden buildup. Aim for nitrate 2–15 ppm in mixed reefs. Keep phosphate near 0.03–0.10 ppm. If those climb with steady feeding, detritus is often the source.
- Common trap zones: behind rocks, sump baffles, and dead corners
- Early signs: film algae, cyano patches, and cloudy puffs
- Helpful tools: turkey baster, flashlight, and small powerhead
Build a flow and filtration plan that exports waste
Start with flow that keeps particles suspended. Target 20–40x display turnover per hour. Use two pumps for crossflow and random pulses. Point flow to sweep behind rocks, not at coral flesh.
Mechanical filtration should catch what flow lifts. Filter socks work best at 100–200 microns. Swap or rinse them every 2–3 days. A neglected sock becomes a nutrient reactor.
A protein skimmer removes organics before they decay. Tune it for a steady, dark tea skimmate. Empty the cup twice weekly. Clean the neck weekly for stable foam.
In the sump, aim for a simple “dirty to clean” path. Place the drain into socks or a roller. Then skimmer section, then refugium or media, then return. If you need help sizing gear, see reef tank sump setup.
- Flow target: 20–40x turnover, with random pulses
- Filter socks: 100–200 microns, cleaned every 2–3 days
- Skimmer: clean neck weekly, cup twice weekly
Hands-on maintenance: siphon, stir, and troubleshoot
Plan a weekly detritus routine around water changes. Siphon 10–20% of tank volume each week. Use a gravel vac on bare areas and the top 1 cm of sand. Avoid deep stirring in older beds.
Before siphoning, blow rocks with a baster or powerhead. Wait five minutes for particles to lift. Then run your sock or roller to catch them. This method works well in SPS systems with high flow.
Feed with intent to reduce waste. Rinse frozen food in RO water. Feed smaller portions twice daily. Remove nori clips after four hours. For smarter feeding, read reef fish feeding guide.
Common mistakes cause recurring buildup. Overpacked rock blocks flow and traps mulm. Low return flow leaves sump debris untouched. Dirty media bags leach nutrients back. If cyano persists, review cyano in reef tank for targeted fixes.
- Weekly: baste rocks, then siphon 10–20% with the change
- Sand: vacuum the surface only, especially in tanks over one year old
- Food: rinse frozen cubes and remove uneaten nori within four hours
Detritus control is a system, not one tool. Use strong, smart flow and fast mechanical capture. Pair that with steady siphoning and careful feeding. Your reef will look cleaner and stay more stable.
Sources: Holmes-Farley, R. (Reefkeeping Magazine) nutrient control articles; Delbeek & Sprung, The Reef Aquarium (Vol. 1–3); Fenner, The Conscientious Marine Aquarist.
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