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Coral Care

Coral Care 101: Keeping Your Corals Healthy

Learn the four pillars of coral health — light, flow, water chemistry and feeding — plus how to acclimate new frags and spot trouble early.

By Delightful Coral 2 min read
Illustration representing coral care fundamentals
Illustration representing coral care fundamentals

Healthy coral comes down to four things done consistently: light, flow, water chemistry, and feeding. Get those right and most corals will reward you with color and growth. Here’s how to think about each.

1. Light

Corals host photosynthetic algae (zooxanthellae) that feed them in exchange for light. Too little and corals brown out and starve; too much and they bleach. The trick is matching intensity to the species:

  • Soft corals & LPS — low to moderate light, often lower in the tank.
  • SPS corals — high light, usually higher up and closer to the fixture.

Acclimate corals to new lighting gradually over two to three weeks rather than blasting them on day one.

2. Flow

Water movement delivers nutrients, removes waste and prevents detritus from settling on coral tissue. Aim for turbulent, random flow rather than a firehose pointed at one spot. If a coral’s polyps are flattened and can’t extend, the flow is too strong; if detritus collects on it, too weak.

3. Water chemistry

Corals build skeletons from calcium and carbonate, so stable chemistry is non-negotiable. The big three:

  • Alkalinity: 8–9 dKH
  • Calcium: 400–450 ppm
  • Magnesium: 1300–1400 ppm

We cover this in depth in our water chemistry guide. The headline: keep them stable. A steady 7.5 dKH beats a value that bounces between 7 and 11.

4. Feeding

Photosynthesis isn’t the whole story — many corals also capture food. LPS corals like Acans and Euphyllia happily take meaty foods (mysis, coral pellets) a couple of times a week. Feeding boosts growth and color, but feed sparingly to avoid fouling the water.

Acclimating new coral

New frags are stressed from shipping. Acclimate them carefully:

  1. Float the bag to match temperature (~15 minutes).
  2. Drip acclimate to match water chemistry over 30–45 minutes.
  3. Dip in a coral dip to kill hitchhiking pests.
  4. Place low in the tank, then move up gradually as it settles.

Reading the warning signs

Corals tell you when something’s wrong — learn the language:

  • Browning — often too little light or excess nutrients.
  • Bleaching (going pale/white) — light shock, heat, or chemistry swings.
  • Receding tissue — a serious sign; check parameters and for pests.
  • Closed up for days — stress, irritation, or poor water quality.

Catch these early and most are reversible. Start with hardy species while you build your instincts — see our best beginner corals list, and shop healthy, quarantined frags when you’re ready.