My Corals Aren't Doing Well

My Corals Aren't Doing Well — What Should I Check?

A coral that stays closed, loses color or stops growing does not automatically need a supplement or medication. Start with the basics: water parameters, lighting, nutrients and flow.

Start with the simple things.

Most coral problems can be narrowed down by checking these four areas before making major changes to the aquarium.

1
Parameters Is the water stable?
2
Lighting Does the coral have enough PAR?
3
Nutrients Not too high — or zero
4
Flow & Placement Check the coral's location
1

Check Your Reef Parameters

Before changing lighting or adding supplements, make sure the basic water parameters are appropriate and reasonably stable.

Salinity 1.025–1.026
Temperature 77–79°F
Alkalinity 8–9 dKH
pH 8.0–8.4

Consistency matters. A coral will generally respond better to stable parameters than to an aquarium where the numbers are constantly being adjusted in an attempt to make them perfect.

View the Wet Pets Reef Tank Parameters Guide
2

Check the Lighting

Corals need light for the photosynthetic organisms living within their tissue. A light can appear extremely bright to us while still providing too little usable light to the coral — or too much.

The best way to know is to measure PAR at the location where the coral is actually sitting.

Wet Pets PAR Meter Loaner

Wet Pets has a PAR meter available for customers to borrow so you can measure the actual light levels throughout your reef aquarium instead of guessing.

Soft Corals Approximately 50–100 PAR
Most LPS Approximately 75–150 PAR
Most SPS Approximately 150–300+ PAR
These are general starting ranges. Individual coral species can prefer more or less light. If a coral needs to be moved to substantially stronger lighting, increase its exposure gradually rather than immediately placing it under maximum intensity.

Wet Pets Recommended Reef Lighting

For reef aquariums, the AI Blade Coral Grow is a simple, low-profile lighting option designed around the wavelengths used for coral photosynthesis. Blade fixtures also provide broad, even coverage that helps reduce severe hotspots and shadows.

Primary Coral Lighting The Blade Coral Grow is the model we recommend as the primary Blade for providing usable coral light and PAR. AI Blade Coral GROW
Supplemental Color Blade Coral Glow can be added alongside Grow lighting for additional blue/UV fluorescence and coral coloration. AI Blade Coral GLOW
Lighting: AI Blade Coral Grow · AI Blade Coral Glow
3

Check Nitrate & Phosphate

Reef aquariums need nutrients. The goal is not to keep nitrate and phosphate at zero.

Nitrate — NO₃ 2–15 ppm General mixed reef target
Phosphate — PO₄ 0.03–0.10 ppm General mixed reef target

Very high nutrients can contribute to algae growth and other problems, but repeatedly maintaining nitrate or phosphate at zero can also cause corals to become pale, lose vigor or struggle.

If nutrients are low, increase them gradually. If they are high, reduce them gradually. Avoid making sudden corrections.

For low nutrients: Brightwell NeoNitro · Brightwell NeoPhos
NeoNitro / NeoPhos Dosing Calculator
4

Check Flow & Placement

Even when parameters and lighting are correct, a coral may simply be unhappy with its location.

  • Make sure the coral is not receiving a constant hard stream directly from a wavemaker.
  • Look for tissue being violently blown to one side or pulled away from the coral's skeleton.
  • Make sure another coral is not touching or stinging it.
  • Check whether the coral is being shaded by rockwork or another coral.
  • If the coral was recently moved, give it time to adjust before moving it again.

What Is the Coral Telling You?

Don't judge the aquarium from a single moment. Look for a trend over several days.

Good Signs Normal extension, stable coloration, inflation and visible new growth.
Needs Attention Staying closed for days, gradual fading, unusual shrinking or noticeable loss of tissue.
Urgent Rapid tissue loss, exposed fresh skeleton, brown jelly-like material or a problem spreading quickly through the coral.
Don't change everything at once. If you simultaneously change lighting, flow, alkalinity, nutrients and dosing, it becomes nearly impossible to know what helped or hurt the coral. Correct obvious problems first, make changes gradually, and watch how the coral responds.
Simple Coral Troubleshooting Order:

Parameters → PAR / Lighting → Nitrate & Phosphate → Flow / Placement
If all four look appropriate and the coral continues to decline, look more closely for pests, physical damage, coral aggression or disease.

Coral requirements vary by species, so these values are intended as beginner-friendly mixed reef guidelines rather than absolute rules. If you are unsure why a coral is declining, take a clear photo of the coral along with your alkalinity, nitrate, phosphate and salinity results to Wet Pets Aquatics. If lighting may be the problem, ask us about borrowing the Wet Pets PAR meter.