Feeding Corals: What, When, and How Much

Ask ten reefers whether you need to feed corals and you will get ten different answers, ranging from "never — light is enough" to elaborate nightly target-feeding rituals. The truth sits in the middle and depends entirely on what you keep. Photosynthesis covers most of a coral's energy budget, but research on wild reefs shows heterotrophy — actual eating — can supply 15–35% of daily carbon for many species, and far more for large-polyp corals. Fed corals grow faster, color up better, and recover from stress more reliably. Here is what to feed, when, how much, and how to do it without turning your tank into a nutrient swamp.

Do Corals Actually Need to Be Fed?

Every photosynthetic coral runs on two engines. The zooxanthellae living in its tissue convert light into sugars, covering the baseline energy budget. The coral's polyps capture prey — zooplankton, bacteria, dissolved organics — which supplies the nitrogen, phosphorus, and amino acids that light alone cannot provide. Sugar is fuel; food is building material.

That distinction explains the practical answer. A tank of soft corals and a few hardy LPS with fish being fed daily will do fine on incidental capture alone: fish waste, leftover flake, and the plankton every mature tank produces. But if you want a torch coral to grow new heads this year instead of next year, or an Acropora colony to hold deep coloration, direct feeding is the difference between surviving and thriving. Non-photosynthetic corals — sun corals (Tubastraea), Dendrophyllia, most gorgonians with white or brightly colored polyps — have no light engine at all and will starve without feeding several times per week. Skip NPS corals entirely unless you are ready for that commitment.

Matching Food Particle Size to Polyp Size

The single most common feeding mistake is size mismatch. A coral can only eat what its polyps can capture and swallow, and offering the wrong size wastes food and fouls water.

• Large-polyp corals (torch, hammer, frogspawn, Duncans, Acans, chalices, sun corals): meaty foods 1–4 mm — mysis shrimp, krill pieces, LPS pellets, chopped silverside. A Duncan will happily take a whole mysis; a large Acan lord can handle a chunk of krill.
• Medium-polyp corals (Blastomussa, Favia, Goniopora to a degree): baby brine shrimp, cyclops, 200–800 micron pellet or powder blends.
• Small-polyp corals (Acropora, Montipora, Stylophora, most zoanthids): 5–300 micron foods — rotifers, oyster eggs, powdered planktonic blends like Reef-Roids or Benepets, and amino acid supplements they absorb directly from the water.
• Filter feeders (feather dusters, clams over 3 inches mostly self-feed; smaller clams and some gorgonians): live or preserved phytoplankton, 1–20 microns.

Frozen foods should be thawed in a cup of tank water first; the rinse-or-not debate is really a nutrient question — rinsing reduces phosphate input from the packing juice, but that juice is also exactly what SPS and filter feeders eat. In a high-nutrient tank, rinse; in a bottomed-out tank, feed juice and all.

Feeding LPS Corals: The Biggest Payoff

Large-polyp stony corals show the most dramatic response to feeding of anything in the hobby. A target-fed torch or hammer can double its growth rate versus an unfed one, and Acans visibly inflate and expand within weeks of a regular schedule. If you keep euphyllia, our torch coral care guide covers placement and flow; feeding is the other half of that equation.

The technique: feed 30–60 minutes after lights-out or during the dusk period, when feeding tentacles extend. Turn off return and wavemaker pumps (or use feed mode), thaw a cube of mysis in tank water, and deliver 1–3 pieces per head with a turkey baster or pipette, releasing food an inch upstream so it drifts onto the tentacles rather than blasting them. Wait until the polyp closes over the food before restoring flow — usually 5–10 minutes. Twice a week is the sweet spot for most LPS; even once a week produces visible improvement over months.

Two warnings. First, watch for thieves: peppermint shrimp, hermit crabs, and some wrasses will steal food straight from a coral's mouth, so feed near the fish's normal feeding time or after dark. Second, never force-feed a coral that will not extend tentacles — uneaten meat rotting in a polyp's grip causes tissue infections.

Feeding SPS and Small-Polyp Corals

Acropora and Montipora polyps are around a millimeter across; they cannot take mysis. What they can do is capture fine plankton and absorb dissolved nutrients directly through their tissue. Broadcast feeding is the method here: mix a half-teaspoon of powdered plankton food per 100 gallons in a cup of tank water, kill the return pump but leave a wavemaker on low, and pour the slurry into the flow so it circulates past the colonies for 15–20 minutes. Polyp extension during and after feeding tells you it is working — a well-fed Acropora shows fuzzy full-body polyp extension even under moderate flow.

Frequency: 1–3 broadcast feedings per week is plenty for a mixed reef. Serious SPS keepers with heavy fish loads often skip powdered foods entirely, because a big fish population being fed 2–3 times daily creates a constant rain of fine particles and dissolved food — the fish are the feeding system. Getting food to drift past every colony also depends on circulation; if your powdered food settles in dead spots instead of circulating, your flow needs work before your feeding does — Check price on Amazon.

How Often and How Much: A Realistic Schedule

More corals are harmed by overfeeding's side effects than by hunger. Every gram of food becomes ammonia, then nitrate and phosphate. The schedule below suits a typical mixed reef with a moderate fish load:

Start at the low end and increase only if nutrients stay in range. If you are new to corals entirely, begin with the forgiving species in our easy beginner corals roundup — most of them thrive with zero direct feeding, which lets you learn the nutrient side gradually.

Keeping Nutrients in Check While Feeding

Feeding corals and controlling nutrients are not opposites; they are a paired system. The goal is high food input with high export, which mimics a real reef far better than starving the tank. Target nitrate at 2–10 ppm and phosphate at 0.02–0.1 ppm, and test weekly — a rising trend over three weeks means you increase export, not necessarily that you cut feeding. A complete kit that covers nitrate, phosphate, calcium, and alkalinity in one box makes the weekly habit painless — Check price on Amazon.

On the export side, your skimmer is the workhorse: it removes dissolved organics and uneaten food before they mineralize into nitrate. Skim slightly wetter for 24 hours after heavy broadcast feedings. If your skimmer is undersized or ten years old, upgrading it buys you more feeding headroom than any other single purchase — Check price on Amazon. Round it out with a consistent water change schedule and, in heavily fed tanks, a refugium or GFO.

One more feedback loop worth knowing: heavy coral feeding raises demand on calcium and alkalinity because fed corals calcify faster. If your alkalinity consumption jumps from 0.3 to 0.7 dKH per day after you start a feeding regimen, that is success — adjust your dosing to match.

Signs You Are Getting It Right (or Wrong)

Well-fed corals show it within 4–8 weeks: fuller tissue inflation, faster tip growth on SPS, new heads on euphyllia and Duncans, and richer coloration as amino acids fill out pigment production. Overfeeding shows up in the water before the corals — nitrate climbing past 25 ppm, phosphate past 0.15, film algae accelerating, cyano patches appearing on the sand. If that happens, halve the feeding volume, keep the frequency, and boost export.

You can find our tested picks for skimmers, test kits, and feeding gear on the best gear page. And if you are still building foundational habits — testing rhythms, feeding discipline, stability before ambition — our ebook The First Tank puts the whole first-year system together in one place.

FAQ

Can I overfeed corals directly? The corals themselves rarely overeat — a polyp takes what it can hold and ignores the rest. The danger is everything they do not eat: excess food decays into nitrate and phosphate, fueling algae and stressing the system. Feed measured amounts, watch your weekly test numbers, and let the trend line set your portion size.

Do zoanthids and mushrooms need feeding? No — both are heavily photosynthetic and absorb dissolved nutrients efficiently, so they thrive in most tanks with zero direct feeding. That said, many zoas respond to a weekly broadcast of fine powdered food with faster spreading, and mushrooms will visibly wrap around cyclops or pellet fragments. Treat it as an optional growth accelerator, not a requirement.

Should I turn off my skimmer when feeding corals? For broadcast feeding, yes — run feed mode or switch the skimmer off for 30–60 minutes so it does not strip the plankton out before corals capture it. For target feeding LPS, it barely matters since food goes directly onto the polyp. Just never forget to turn it back on; set a timer or use a controller with a feed-mode function.

What is the best time of day to feed corals? Evening, shortly after the main lights dim. Most corals extend feeding tentacles on a nocturnal rhythm because reef plankton density spikes after dark, so capture rates are dramatically better than at midday. Sun corals and other NPS may need a few weeks of consistent evening feeding before they learn to open on schedule.