Cleaning a reef tank properly means working methodically without disturbing your coral or spiking water parameters. The short version: do partial water changes of 10-15% weekly, clean the glass every few days with a magnetic scraper, and export nutrients through your skimmer and refugium. Avoid cleaning everything at once, because wiping down all your surfaces on the same day strips beneficial bacteria and sends ammonia climbing.
This guide walks through every part of reef tank maintenance, from glass cleaning and substrate care to equipment upkeep and export systems. Whether you have a 50-gallon mixed reef or a 200-gallon SPS tank, the same principles apply.
Glass and Acrylic Panel Cleaning
The most visible part of reef maintenance is keeping the front glass clear of coralline algae and diatom film. If you let coralline calcify for more than two weeks, removing it becomes a real workout.
Magnetic Scrapers for Daily or Every-Other-Day Use
A good magnetic scraper solves the routine film problem without getting your hands wet. The Flipper MAX and the Tunze Care Magnet are two of the most widely used options. The Flipper MAX handles up to 3/4-inch glass and swaps between a felt pad (for light film) and a stainless steel blade (for stubborn coralline). The Tunze 0220.020 is gentler and works well on acrylic panels where metal blades are a bad idea.
Run the scraper across the glass every two or three days. This takes about 90 seconds and prevents the thick buildup that requires blade scrapers and elbow grease.
Removing Calcified Coralline
If coralline has already calcified on the glass, a razor blade scraper works on glass panels. Hold it at a low angle and keep it wet. On acrylic, use a plastic razor blade like the ones sold by Aqueon or a dedicated acrylic scraper. Scratching acrylic with metal blades is permanent, so be careful.
For really stubborn spots on glass, a diluted muriatic acid solution (one part acid to ten parts water, applied with a paper towel while the tank is empty or the glass section is above waterline) dissolves calcium buildup fast. Rinse thoroughly before refilling.
Substrate and Sand Bed Maintenance
Sand beds in reef tanks accumulate detritus, uneaten food, and fish waste. Over time this organic matter fuels nitrate and phosphate spikes that stress coral.
Vacuuming vs. Leaving Sand Undisturbed
This is one of the more debated topics in reef keeping. A shallow sand bed of 1-2 inches should be gently vacuumed during water changes to remove detritus sitting on the surface. Go slow, hover the Python or Lee's vacuum just above the sand surface, and avoid pulling up sand grains.
A deep sand bed (4+ inches) works differently. Deep beds host anaerobic bacteria that process nitrates. Disturbing a DSB can release hydrogen sulfide pockets and cause a tank crash. If you run a DSB, skip the vacuum and let nassarius snails and sand-sifting gobies like the Diamond Goby do the work.
Sand Stirrers Worth Keeping
Nassarius snails are excellent detritivores and will work through your sand surface constantly. Conchs (fighting conchs, not queen conchs) are also useful and safe for reef tanks. A small group of five to ten nassarius snails per 50 gallons is a solid starting point.
Water Change Technique for Reef Tanks
Water changes are your primary tool for exporting dissolved organics, replenishing trace elements, and stabilizing alkalinity.
Frequency and Volume
For a medium bio-load reef, 10-15% weekly is the standard. Heavily stocked tanks or SPS-dominated systems often benefit from 20% weekly. The key is consistency. Skipping two weeks and then doing a 30% change creates parameter swings that stress coral more than a slight excess of nutrients.
Mix saltwater at least 24 hours before use. Freshly mixed salt often has elevated pH and unstable alkalinity. Use a refractometer to confirm salinity at 1.025-1.026 before adding water to the tank.
Temperature and Parameter Matching
Cold water additions cause temperature drops that trigger spawning events and stress. Match the new water to within one degree of your tank temperature. For tanks with SPS coral, match alkalinity within 0.5 dKH of your tank's current level. A two or three point alkalinity swing during a water change will show up as tissue recession at the base of achaeopora and montipora within 24-48 hours.
Equipment Maintenance
Your equipment runs around the clock. Skimmer cups overflow, pump impellers clog, and return pump intakes accumulate detritus if you ignore them.
Protein Skimmer Cleaning
Clean the skimmer neck weekly and the cup every two to three days. A neck coated in dark skim mate reduces skimming efficiency because the film disrupts the air-water interface. A dedicated skimmer neck brush (sold by Two Little Fishies and others) reaches into the body and cleans the reaction chamber walls.
Every month, pull the skimmer completely and soak it in a vinegar and water solution (50/50) for a few hours. This dissolves calcium deposits from the air intake, venturi, and impeller housing. Rinse and run it in fresh RO water for an hour before reinstalling.
Return Pump and Powerhead Care
Return pump impellers and powerhead rotors accumulate calcium and slime over 4-6 months. Decreased flow is the first sign. A monthly vinegar soak keeps impeller housings clear and maintains rated flow.
If you're checking out options for the gear that makes maintenance easier, have a look at our guide to the best fish tank cleaning equipment for a breakdown of scrapers, vacuums, and brushes that actually hold up long-term.
Nutrient Export Systems
Cleaning the glass and changing water is reactive maintenance. Nutrient export is proactive, keeping organics from building up in the first place.
Refugiums and Chaeto Algae
A refugium with chaetomorpha (chaeto) algae is one of the most effective low-maintenance export systems available. Chaeto absorbs nitrates and phosphates as it grows, and you export nutrients by harvesting the algae and throwing it away. A pound of chaeto harvested every two weeks removes more dissolved organics than most skimmers can match.
Keep the refugium light on a reverse cycle from the display tank. This stabilizes pH by ensuring photosynthesis is happening around the clock.
Activated Carbon and GFO
Activated carbon removes dissolved organics and yellowing compounds. A 250mL cup of carbon in a reactor like the Two Little Fishies PhosBan Reactor 150 changes water clarity noticeably within 48 hours. Replace carbon every 4-6 weeks.
Granular ferric oxide (GFO) binds phosphates before coral and nuisance algae can use them. For a 100-gallon reef, 100-150mL of GFO in a reactor keeps phosphate below 0.05 ppm. Change it when your phosphate reading starts climbing back up, typically every 4-8 weeks depending on bio-load.
For a full breakdown of the scrapers and tools that make glass cleaning faster, see our recommendations in the best fish tank cleaning tools guide.
Dealing with Common Algae Problems During Cleaning
Algae outbreaks usually signal a nutrient problem, not a cleaning deficit. But cleaning technique matters too.
Cyano and Dino Outbreaks
Cyanobacteria (red slime algae) forms a suffocating mat over rock, sand, and coral. Physically removing it with a turkey baster and siphon during water changes helps, but the bacteria comes back unless you address the root cause. Low flow over the sand bed is the most common trigger. Add a wavemaker aimed at the affected area and increase water changes to 20% for two to three weeks.
Dinoflagellates (brown stringy algae) are more stubborn. A three-day blackout combined with elevated nutrients (a small piece of shrimp allowed to decompose briefly to fuel bacterial competition) combined with UV sterilization has worked well for many hobbyists. It sounds counterintuitive to add nutrients, but dinos thrive in ultra-low nutrient conditions.
Coralline Algae Maintenance
Purple and pink coralline algae on your rocks and back wall is a good sign. It means your calcium, alkalinity, and magnesium are in range and competition for surface area is working in your favor. Leave coralline on everything except the viewing glass.
FAQ
How often should I clean my reef tank glass? Every two to three days for lightly stocked tanks, daily for tanks with heavy feeding or high silicate in your RO water. Using a magnetic scraper takes under two minutes and prevents coralline from calcifying. Once coralline hardens on the glass, removing it takes significantly more effort.
Can I use a regular aquarium vacuum on a reef tank sand bed? Yes, but technique matters. For a shallow sand bed of 1-2 inches, hover the vacuum just above the surface and pull up detritus without disturbing the sand itself. For deep sand beds over four inches, do not vacuum at all. Deep beds rely on undisturbed anaerobic bacteria for nitrate reduction.
How do I clean a reef tank without killing my corals? Work in small sections and avoid doing all your maintenance tasks on the same day. Never clean your sump filter socks, scrub your rocks, and do a large water change all in one session. Spreading tasks across the week keeps your bacterial populations stable and your parameters from swinging.
What is the best way to clean saltwater residue off the outside of my tank and equipment? White vinegar on a paper towel removes calcium and salt creep from the tank exterior, stands, and equipment housings. For really thick calcium deposits on pump housings and overflow boxes, soak in undiluted white vinegar for an hour or two, then scrub with an old toothbrush.
Key Takeaways
Clean your reef tank glass every two to three days to prevent coralline buildup. Do 10-15% water changes weekly with temperature and parameter-matched saltwater. Clean your skimmer cup every two to three days and do a full vinegar soak monthly. Build a solid nutrient export system with a refugium, carbon, and GFO so that you are removing organics continuously rather than chasing outbreaks. Consistency beats intensity in reef maintenance.