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Corals are famous for housing tiny algae called zooxanthellae. These algae live inside the coral’s tissues and, under light, make sugars via photosynthesis. That is a powerful energy source, but it is not the whole story. In nature and in our aquariums, corals also feed in other ways. They catch plankton, trap tiny particles, absorb dissolved nutrients, and even farm helpful microbes. Understanding these extra feeding strategies helps you keep healthier, faster-growing corals with richer color and fuller polyp extension. This beginner-friendly guide explains how corals feed beyond photosynthesis and how you can support that in your aquarium.
Why Coral Feeding Matters Beyond Zooxanthellae
Photosynthesis can cover a big chunk of a coral’s daily energy budget, but it is rarely 100%. Many species get 10–60% of their energy from eating. For some, especially non-photosynthetic (NPS) corals, feeding is essential for survival. Even light-loving species benefit from supplemental food, which provides proteins, lipids, and critical micronutrients that zooxanthellae cannot fully supply. In aquariums with very clear water, aggressive filtration, and ultra-low nutrients, feeding often becomes the difference between simply surviving and truly thriving.
How Corals Capture and Use Food
Tentacles and Nematocysts: The Classic Coral “Catch”
Most corals have tentacles armed with stinging cells called nematocysts. These cells fire tiny harpoons to stun or grab small prey such as zooplankton. When food contacts the tentacle, cilia (small hair-like structures) help move the prey toward the mouth. You can often see this in your tank when LPS corals like Acanthastrea (Micromussa), Trachyphyllia, or Scolymia inflate and pull meaty bits into the mouth. Many corals extend tentacles more at night because zooplankton is more active after dark.
Mucus Nets and Ciliary Conveyer Belts
Some corals produce a sticky mucus layer that traps tiny particles drifting by. Cilia then drive the trapped particles along the coral’s surface toward the mouth. Think of it like a conveyor belt of snacks. This method is great for catching very fine plankton and “marine snow,” which are too small for tentacles alone. In aquariums, gentle, varied flow helps keep those particles suspended so corals can grab them efficiently without getting blasted.
Mesenterial Filaments: External Digestion on the Reef
Corals can extend digestive filaments, called mesenterial filaments, from their mouths or body wall to break down food outside their bodies. In the wild, these filaments help corals digest captured prey stuck on their surface or even digest organic films on nearby rocks. Sometimes this looks like stringy white threads. In tanks, you may see this during feeding events or coral competitions where one coral tries to digest a neighbor’s tissue. It is a reminder that feeding and aggression often overlap in coral life.
Dissolved Nutrients and Direct Absorption
Corals do not only eat visible particles. They can absorb dissolved organic matter (DOM), amino acids, and inorganic nitrogen sources like ammonium. This process is subtle, but it gives corals a steady trickle of nutrients between larger meals. Many aquarists use amino acid supplements for this reason. While not a replacement for particulate food, dissolved nutrition can improve tissue growth, polyp extension, and coloration when used carefully.
Microbial Partners and “Invisible” Food
Corals host complex communities of bacteria and other microbes in their mucus and tissues. Some of these microbes help process nutrients, convert waste into usable forms, or even become food themselves when shed and re-ingested. In a reef tank, a mature microbiome, live rock surfaces, and a refugium can produce a natural “soup” of micro-life. Corals benefit from this background buffet, which is one reason stable, mature systems often grow corals better than brand-new ones.
What Do Corals Eat? From Plankton to Amino Acids
Phytoplankton vs. Zooplankton
Phytoplankton are microscopic algae; zooplankton are tiny animals like copepods and rotifers. Many corals can take both, but preferences vary by species and polyp size. SPS corals with small polyps usually favor very small particles, often in the 5–50 µm range, which includes many phytoplankton and micro-zooplankton. LPS corals with big mouths can take larger zooplankton, such as copepods, Artemia nauplii, and minced mysis. NPS soft corals and gorgonians often focus on small plankton delivered frequently.
Marine Snow and Detritus
Marine snow is a mix of dead plankton, bacteria, mucus, and waste that naturally drifts in the ocean. On reefs, corals capture this steady rain of particles. In aquariums, we create a version of marine snow through feeding, bacterial plankton, and microfauna reproduction. Fine particle foods and feeding live or preserved plankton help mimic this. Cloud-like feedings that gently pass over corals are often more effective than dropping large chunks that fall to the sand.
Amino Acids, Fatty Acids, and Trace Nutrients
Corals need building blocks for tissue growth, not just energy. Amino acids support protein synthesis, and essential fatty acids support membranes and energy storage. Some commercial coral foods and additives target these needs. Used in moderation, they can improve growth and color. However, dosing without a plan can raise nutrients too quickly. Always start low and observe your corals’ response.
Match Particle Size to Coral Type
Particle size is one of the most important details in coral feeding:
– SPS (Acropora, Montipora, Pocillopora): Prefer tiny suspended foods (5–100 µm). Powdered coral foods, rotifers, and phytoplankton blends work well. Overly large foods are ignored or blow away.
– LPS (Euphyllia, Acanthastrea/Micromussa, Trachyphyllia, Scolymia): Accept larger pieces (100–1000 µm). Finely chopped mysis, shrimp, or specialized LPS pellets are ideal. Feed pieces sized for the polyp to swallow without struggling.
– Soft corals (Sarcophyton, Sinularia, Kenya tree) and zoanthids/palythoa: Often benefit from fine plankton and dissolved nutrition. Some will take tiny meaty bits, but they generally prefer small particles.
– NPS corals (Tubastraea/sun corals, many gorgonians, Dendronephthya): Require frequent planktonic foods; sun corals also take larger meaty items. Dendronephthya are extremely demanding, needing constant streams of fine plankton.
Feeding Strategies in the Aquarium
Broadcast Feeding: The Reef “Snowstorm”
Broadcast feeding means dispersing small foods throughout the tank so everything gets a taste. For SPS and many soft corals, this is the main method. Mix powdered foods, rotifers, or phytoplankton with tank water, then gently pour or baste it into high flow so it drifts through the reef. Run pumps to keep particles suspended. Start with small amounts, watch the corals, and adjust frequency based on polyp extension and nutrient levels.
Target Feeding: Precision for LPS and Select Species
Target feeding uses a pipette or turkey baster to place food directly on a coral’s mouth or tentacles. This is great for LPS and sun corals that can handle bigger pieces. Turn off return and skimmer for 15–30 minutes, reduce flow if needed, and gently cover the polyp with a small cloud or a single piece of food. Watch for the feeding response: the mouth closes and tentacles pull food inward. Avoid overstuffing; one or two well-sized pieces per polyp is enough.
Continuous Feeding for NPS Corals
Non-photosynthetic corals need frequent small meals. Instead of big feeds once or twice a week, they do better with multiple daily feedings or a continuous slow dose of planktonic foods. Some aquarists use a dosing pump or drip system to add a diluted mix of rotifers and phytoplankton. A skimmer and regular maintenance are essential to keep nutrients under control in NPS systems.
Timing and Flow: When and How to Feed
Many corals extend polyps more at night, so evening feedings often work best. Try dimming your lights or feeding during the ramp-down period to encourage polyp extension. Use moderate, random flow to keep food in motion, but not so strong that it blows food off corals. After feeding, wait 15–45 minutes before turning the skimmer back on so corals can ingest what they caught.
Tools and Techniques That Make Feeding Easier
Useful tools include a turkey baster, long pipette, feeding ring (to keep floating food in one area), and a small cup for mixing food with tank water. Rinse frozen foods with RO/DI water if you are trying to reduce phosphate. For target feeding, train fish to stay busy by feeding them at the opposite side of the tank first. This gives corals a head start before fish steal their meal.
Species-Specific Guidance
SPS Corals: Acropora, Montipora, and Friends
SPS corals have small mouths and prefer tiny foods suspended in the water. Broadcast feeding 2–4 times per week with fine coral foods, rotifers, and mixed phytoplankton works well. Many hobbyists also dose amino acids lightly. Observe polyp extension: stronger extension during or after feeding is a good sign. Keep nutrients stable; SPS are sensitive to swings. Even modest supplemental feeding can improve color, thickness of tissue, and branching growth.
LPS Corals: Euphyllia, Acanthastrea/Micromussa, Trachyphyllia
LPS corals often show dramatic feeding responses. You can feed small pieces of mysis, brine shrimp enriched with spirulina, or LPS pellets 1–2 times per week. For Euphyllia (hammer, frogspawn, torch), use very small portions to avoid tearing tissue and to prevent food rotting between tentacles. For meatier corals like Trachyphyllia and Scolymia, a pea-sized piece per feeding is enough. Regular moderate feeding supports inflation, faster growth, and resilience to stress.
Soft Corals and Zoanthids
Softies like toadstools and leathers primarily benefit from fine particles and dissolved nutrition. They may not capture big chunks, but they do well in tanks with consistent micro-plankton availability. Zoanthids and palythoa can accept very small meaty bits but mostly rely on small particles and good water chemistry. Safety note: some zoanthids and palythoa can contain palytoxin. Avoid touching them with bare hands, and never expose them to hot water vapor (for example, when cleaning). Use gloves and eye protection when fragging.
Non-Photosynthetic Corals: Sun Corals, Gorgonians, and Challenging Filter Feeders
Sun corals (Tubastraea) love meaty foods and should be target fed several times per week, ideally at night when polyps open. Non-photosynthetic gorgonians and feather-like soft corals prefer a constant supply of tiny plankton; they rarely succeed with occasional large meals. Dendronephthya and similar species are advanced-only corals, often requiring near-constant fine plankton and very strong flow. If you are new to NPS, start with sun corals or hardier NPS gorgonians before attempting the most demanding species.
Balancing Feeding With Water Quality
Nutrients: Nitrate and Phosphate
Feeding raises nutrients. Some nitrate (NO3) and phosphate (PO4) are necessary for vibrant corals, but too much can fuel algae and stress sensitive species. Aim for stable ranges rather than chasing exact numbers. Many successful reefers keep nitrates around 5–15 ppm and phosphate around 0.03–0.1 ppm, but your system may differ. Test weekly, adjust feeding amounts, and use export methods like protein skimming, refugiums, and regular water changes.
Skimming, Mechanical Filtration, and Refugiums
Protein skimmers remove dissolved organics and help oxygenate the water, which is especially important if you feed often. Consider pausing your skimmer for a short window during feeding so it does not strip out suspended foods immediately. Filter socks and rollers can be turned off briefly, but remember to turn them back on to avoid nutrient spikes. A refugium with macroalgae can help buffer nutrient rises from heavy feeding.
Avoid Overfeeding and Watch for Pests
Excess food can break down into waste, leading to algae blooms, cyanobacteria, or dinoflagellates. It can also attract pests like bristle worms in large numbers. Feed small portions, monitor how quickly food is eaten, and siphon leftovers if needed. When using live foods, quarantine or purchase from trusted sources to avoid introducing unwanted hitchhikers.
Signs Your Feeding Is Off
Underfeeding: pale colors, thin tissue, weak polyp extension, slow growth, or receding edges. Overfeeding: rising nitrates/phosphates, algae issues, cloudy water, bacterial blooms, or corals producing excess mucus. Adjust slowly, change one variable at a time, and track observations to find your tank’s balance.
Practical Feeding Plans You Can Try
A Simple Mixed-Reef Weekly Schedule
Day 1: Broadcast feed fine coral food (SPS/softies). Turn off skimmer for 30 minutes. Keep moderate flow. Feed fish lightly afterward so they do not steal coral food.
Day 2: Target feed LPS (small mysis or pellets). Dim lights or feed at dusk for stronger feeding response. Restore filtration after 30–45 minutes.
Day 3: Rest day (no coral feeding). Test nitrate and phosphate midweek and log results.
Day 4: Broadcast feed rotifers and phytoplankton blend. Add a light amino acid dose if you use them (follow the lowest recommended dose).
Day 5: Target feed selective corals that looked hungry or are recovering from stress. Keep portions small and watch polyp inflation.
Day 6: Optional light broadcast feed if nutrients are in range and corals show strong extension.
Day 7: Rest day and maintenance. Clean skimmer cup, change or rinse filter socks, and do a small water change if nutrients creep up.
NPS-Focused Nano Tank Plan
Morning: Dose a small amount of phytoplankton and rotifers via a pipette or dosing pump. Keep flow high and random so food stays suspended.
Afternoon: Another small plankton dose. Feed any sun corals a few tiny meaty pieces 2–3 times per week. Watch nutrient levels closely.
Evening: Final small plankton dose. Run a strong skimmer and plan frequent, small water changes. Consider a refugium or algae reactor for nutrient control.
Tips to Improve Coral Feeding Success
Encourage Polyp Extension
Many corals respond to scent cues. Add a small amount of food to the water first to trigger a feeding response, wait a few minutes, then add the main portion. Reducing light intensity during feeding can also help night feeders extend polyps.
Use the Right Flow Pattern
Alternating or random flow helps keep particles suspended and gives every coral a turn at the buffet. If flow is too strong, food flies past; if too weak, food drops to the sand. Adjust pumps to create a gentle “snowfall” that circulates through the reef structure.
Size and Cleanliness Matter
Cut larger foods into coral-sized pieces. Rinse frozen foods if you are battling high phosphates. Remove uneaten chunks after 30–60 minutes. Target feeding with a pipette can reduce waste compared to dumping food in all at once.
Observe and Adjust
Corals “tell” you how they feel. Look for faster feeding responses, better inflation, richer color, and steady growth tips on SPS. If you see stringy brown slime or repeated regurgitation, the pieces are too large or the coral is overwhelmed. Scale back and try finer foods.
Beginner FAQs
Do all corals need to be fed?
No, but most benefit from it. SPS and many soft corals can survive on light and water nutrients, yet feeding improves growth and color. LPS often do noticeably better with regular feedings. NPS corals must be fed to live.
How often should I feed?
For a typical mixed reef, 2–4 light feedings per week work well. For LPS, target feeding 1–2 times per week is common. For NPS, multiple small feeds per day or a continuous low-dose approach is best.
Will feeding ruin my water quality?
Not if you balance it. Feed small amounts, give corals time to eat, then resume filtration. Use a skimmer, refugium, and regular water changes. Test nitrate and phosphate weekly and adjust the plan as needed.
What is the best coral food?
There is no single best option. Use a mix: fine powdered foods for SPS and softies, rotifers and phytoplankton for small-polyp feeders, and small meaty foods for LPS and sun corals. Rotate foods to cover diverse nutritional needs.
Can I feed corals during the day?
Yes. Many aquarists get good results at dusk when polyps start to extend. If a coral is a night feeder, dim the lights or feed later for better responses.
Common Mistakes to Avoid
Overfeeding Large Chunks
Stuffing big pieces into LPS mouths can cause them to spit food back out or develop bacterial issues. Feed smaller, manageable pieces. One or two bites per polyp are plenty.
Ignoring Flow During Feeding
No flow means food settles and rots. Too much flow sweeps food away. Find the “just right” balance where food suspends and gently passes through coral tentacles.
Feeding Without Testing
As you increase feeding, test nitrate and phosphate. If nutrients spike, reduce feeding, boost export, or increase maintenance. Stability is more important than any single number.
Assuming Light Alone Is Enough
Even with strong lighting, many corals still want food. Supplemental feeding can turn average growth and color into excellent results, especially in ultra-clean tanks.
A Closer Look at Nighttime Behavior
Sweeper Tentacles and Territory
At night, some corals extend long sweeper tentacles to capture food and defend turf. These can sting neighbors and can be mistaken for feeding tentacles. Give aggressive species like some LPS extra space to avoid damage, and target feed without encouraging conflict with nearby corals.
Feeding Cues and Conditioning
Corals learn your routine. If you feed at the same time each evening, many will extend polyps ahead of time in expectation. Use this to your advantage for more efficient feeding and less waste.
Putting It All Together
A strong coral-feeding plan combines several ideas: small, frequent particles for SPS and soft corals; targeted bites for LPS; steady micro-foods for NPS; controlled nutrients and strong export; and careful observation. Over time, you will discover what your specific mix of corals prefers. Remember, the goal is not to “stuff” corals but to provide the right foods in the right sizes, delivered in a way they can capture and digest comfortably.
Conclusion
Beyond their partnership with zooxanthellae, corals feed in many fascinating ways: stinging and catching zooplankton, trapping particles with mucus, digesting food on their surface, absorbing dissolved nutrients, and harvesting the benefits of helpful microbes. In our aquariums, we can support these natural strategies with smart feeding practices. Use fine planktonic foods for small-polyp corals, offer appropriately sized pieces to LPS, and provide frequent micro-feeds for NPS species. Balance feeding with solid filtration and regular testing, and always watch how your corals respond. With patience and consistency, you will see fuller polyp extension, better coloration, stronger growth, and a reef that looks more alive and natural—because you are feeding corals the way nature intended.