If there are very few illness symptoms, but a lot of possible causes how can you know what’s wrong?


It’s no secret that non-moving or sessile (attached to the substrate) saltwater aquarium invertebrates are notorious for being difficult to diagnose if things go wrong, this is especially true for photosynthetic anemones and corals.

saltwater saltwater aquarium coral problems

Usually stress is the cause of coral problems.

Often non-moving invertebrates do not display obvious symptoms like fish do  which are specific to a particular problem. This lack of an obvious link between symptom and cause can make correcting the problem difficult.

When things go wrong many just retract their polyps, wilt and gradually turn to slime.

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Stress is the cause of most problems!

Up to 80% of invertebrate symptoms are simply a result of stress usually caused by poor or fluctuating water quality or incorrect lighting, this is the case most of the time. However there are some pretty nasty coral pests,predators and diseases out there that you need to be aware of…Most of these will not often show up in an aquarium where the new corals have been acclimated correctly, dipped in freshwater and then have been quarantined for 30 days before placing them into the display tank.

problems with corals

If your coral has got a problem; it’s most likely reacting to a stressful situation

Stress is the number one killer of corals and other invertebrates, believe it or not. Not diseases, pests and predators.

So, lets look at the major forms of stress in order of likelihood that these are affecting your invertebrate?

1. Poor/fluctuating water quality (usually temperature and pH, phosphates, nitrates induced stress).
2. Incorrect or inappropriate lighting (bulbs too old, too new, too close or too far away).
3. Not enough water movement (you can never have enough of this in my opinion).
4. Incompatible tank mates (caused by predation, chemical turf wars, other physical damage).
5. Starvation (feeding with supplements really helps sessile invertebrates out and massively reduces the liklihood of starvation).
6. Physical damage (caused by collection, handling, pests, parasites, predation).

This coral is sick

Usually if you get rid of the factor causing the stress the coral will bounce back.

Stress causes the following major symptoms in corals and other sessile invertebrates

1. Tissue recession (or degeneration).
2. Slowing or stopping of growth.
3. Coral Alleopathy (chemical warfare between invertebrates).
4. Lack of polyp expansion in corals, collapsing of anemones.
5. Bleaching of tissue in corals/photosynthetic anemones.

All these symptoms can be fully recovered from if the stressor is identified (start by testing the water quality!) then kept to a minimum. Recovery will be sped up if the affected invertebrate is well fed.

So to diagnose your invertebrates problem start by:

  • checking your water parameters at least 4 times over a 48 hour period to rule out incorrect chemistry and fluctuations over time.Then check your lighting in terms of bulb age and appropriate distances to marine life; check the literature for this.
  • Whether or not you have enough water movement.
  • Are you supplementary feeding? This can really help your invertebrate live thrive.
  • Finally check for incompatibility in your tank and who could be causing any physical damage; if there is any.

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Andrej Brummer #Saltwater Scientist
Saltwater Aquarium Advice Scientist