A reef sand bed can trap waste over time. A careful siphon removes detritus without stripping helpful bacteria. This guide shows a safe, repeatable method.
Choose the right siphon method for your sand
Start by checking your sand depth and grain size. Shallow beds are under 2 inches. Deep sand beds are 4 inches or more. Fine sand blows around with strong suction.
For shallow beds, you can vacuum the top layer. Aim for 0.25 to 0.5 inches per session. This removes trapped food and fish waste. It also limits nutrient spikes.
For deep sand beds, avoid deep stirring. Deep layers can hold low oxygen zones. Disturbing them can release hydrogen sulfide. Instead, skim detritus from the surface only.
Pick a siphon tube that matches your tank size. Use a 1/2 inch tube for 20 to 75 gallons. Use 3/4 inch for 75 to 180 gallons. Add a gravel vac bell for coarse sand.
- Turn off wavemakers and return pump during siphoning.
- Keep a filter sock ready for cloudy water events.
- Plan to siphon 10% to 20% water each session.
If you fight recurring detritus, review flow patterns. Dead spots collect waste behind rock. Try adjusting pumps before you vacuum harder. See reef tank flow basics for placement ideas.
Step-by-step: siphon without losing sand or livestock
Use a bucket marked in gallons or liters. Match new saltwater to 1.025 specific gravity. Keep temperature within 1°F of the tank. Aim for 77°F to 79°F in most reefs.
Start the siphon into the bucket. Hold the tube vertical over the sand. Let detritus lift and tumble inside the tube. Pinch the hose to control suction as needed.
Work in small zones each week. Clean 20% to 30% of the sand surface per session. Rotate areas to protect microfauna. This keeps the bed active and stable.
Watch for snails, hermits, and small fish. Use a mesh strainer over the bucket if needed. Return any hitchhikers to the tank. If sand enters the hose, lift the tube slightly.
- Hover 1/2 inch above fine sand to skim mulm.
- Dip 1 inch into coarse sand to pull debris out.
- Stop when the bucket hits your planned change volume.
After siphoning, restart equipment in order. Turn on the return pump first. Then start heaters and skimmer. Wait 10 minutes before enabling wavemakers. This reduces microbubbles.
Test after the change if your tank is sensitive. Check nitrate and phosphate the next day. Many reefs do well at 2 to 15 ppm nitrate. Aim for 0.03 to 0.10 ppm phosphate. Compare results with your baseline logs.
If you need a routine, pair siphoning with maintenance. Use weekly reef tank maintenance checklist to stay consistent. Consistency prevents sudden swings.
Troubleshooting common problems and mistakes
Cloudy water is common with fine sand. It usually clears in a few hours. Run a 100 to 200 micron filter sock. Replace it after it clogs. Activated carbon can help with odors.
If nutrients rise after cleaning, you may have stirred too deep. Reduce depth on the next session. Clean smaller zones each time. Also check for overfeeding and weak skimming.
Cyano on sand often returns after siphoning. It thrives in low flow and high organics. Increase random flow across the bottom. Keep phosphate from bottoming out. Ultra-low phosphate can worsen cyano in some tanks.
Sand storms happen when pumps restart. Aim powerheads slightly upward. Use a 5 to 10 minute ramp if your controller allows it. Consider heavier grain in high flow reefs. See choosing reef sand grain size for options.
- Do not deep vacuum a 4 inch sand bed in one session.
- Do not clean the entire sand bed on the same day.
- Do not siphon right after dosing bacteria or coral foods.
Sources: Fenner, R. (2001) The Conscientious Marine Aquarist; Delbeek, J.C. & Sprung, J. (1994–2005) The Reef Aquarium Vol. 1–3; Holmes-Farley, R. (2003–2006) Aquarium chemistry articles.
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