Some Signs of a Sick Fish, by Dr. Adrian Lawler

Some Signs of a Sick Fish

by Dr. Adrian Lawler
(retired) Aquarium Supervisor (l984-l998) J. L. Scott Aquarium Biloxi, Ms 39530
Original to Aquarticles

Signs of fish disease (or fish stress) can be any abnormal behavior or any change in fish observed externally. Internal signs of disease can be ascertained by dissection of a living anesthetized fish or a dead/sacrificed fish. Disease organisms or parasites can rapidly increase in numbers in a closed, recirculating small environment as a tank. One should closely observe the fish and tank in order to ascertain any possible problem before a valuable specimen, or a tank, is lost. Daily tank checks should be done to observe for problems. Following is a list of some of the signs one may observe (in freshwater to salt water tanks) indicating a possible problem, with notes, or some possible causes (all causes may not be listed), listed in parentheses (no parentheses indicates fish disease signs may be caused by a number of causes).

Tank Signs (conditions which could indicate present, or future problems with fish)
----Cloudy water (ammonia, bacteria, algae bloom, dinoflagellates [free-living or parasitic], air off, filter
      off, decaying organics, hole in substrate over under gravel filter, suspended particulates)
----Protein foam on surface of water (fish, squid, etc. cut up for food not washed well, excess food in
      tank, something organic decaying in tank)
----Hole exposed to under gravel filter (allows water to bypass substrate and decrease biological
      filtration)
----Missing or dead specimens, which could be decaying in tank and on the way to fouling tank or
      causing a bacteria or algae bloom
----Uneaten or excess food in tank; dying plants; sheds from crustaceans (could foul tank, etc)
----Air off, filter or other support equipment not working correctly (could lead to decline in biological
      filtration and disease control, and result in future tank problems)

Fish Behavior
Movements
----Violent reaction of thrashing, darting, and dying mid-gasp (pH shock or quickly lethal toxins)
----Shimmy (staying in one place and moving side to side) (Bacteria, missing salts)
----Equilibrium decreased, cannot maintain normal position in water (bacteria, dinoflagellates, toxins)
----Scratching on objects in tank (bacteria, parasites, toxins)
----Twitching (bacteria, parasites, toxins, skin irritant)
----Spastic, uncoordinated movements
----Sluggish, lethargic
----Swimming with head up, tail down, at surface
----Constant swimming at surface (dinoflagellates [free-living or parasitic], toxins, pH shock)
----Trying to jump out of tank (dinoflagellates [free-living or parasitic], pH shock, toxins)
----Sticking head out of water and squirting (black-flushing gills) water (dinoflagellates, gill problems)
----Normally bottom fish now at surface
----Normally mid-water or surface fish now at bottom
----Normally hiding fish now out and visible
----Lying on bottom and gasping (near death; heavy bacteria, parasite or dinoflagellate infection)
----Swimming to top, then sinking to bottom

Breathing, opercules, gills
----Gasping, irregular opercular beat, rapid opercular beat (bacteria, dinoflagellates, parasites, toxins)
----Squirting water (parasitic dinoflagellates, gill parasites, gill infection)
----Opercules flared (gill parasites, gill infection, toxin damage to gills, or large gill parasite, as isopod)
----Mouth not closed (usually indicates gill/oxygen problem of some sort, heavy gill infection/infestation;
something caught in buccal cavity or throat = food, substrate, etc)
----Rapid or irregular opercular beat (bacteria, dinoflagellates [free-living or parasitic], toxins,
hyperplasia, parasites )

Eating
----Not eating (bacteria, parasites, toxins, severe liver damage, internal injury or problem, cancer)
----Losing weight even though eating (Mycobacterium, toxins [possibly at time of collection]
----resulting in liver damage)

External Signs
Skin and fins
----Clamped fins (poor water quality, parasites)
----Sunken belly, thin (starved, bacteria, parasites, toxins, liver damage)
----White spots on skin/fins (lymphocystis, bacteria, fungus, dinoflagellates, parasites)
----Fish tissue extensions (various-shaped growths), abnormal growth from skin, fins, etc (hyperplasia,
      tumor-benign or cancer)
----Dark spots in skin (embedded larvae of digenetic trematodes)
----Bloody spots or streaks or sores on skin/fins, lateral line pits (lymphocystis, bacteria, parasites,
      toxins)
----Bloated belly, scales raised from scale pockets (dropsy, kidney damage, tumor-benign or cancer)
----Body deformed, twisted, etc (genetic, injury in egg, vitamin/mineral deficiency, old age, etc)
----Fight (or collection) injuries on skin/fins; frayed fins/scale loss (injuries may lead to viral, bacterial, or
      fungal infections)
----Increase in mucus production; whitish slime (bacteria, fungus, parasites, irritants, toxins)
----Easily visible living objects on skin (parasites, as: leeches, copepods, Argulus, isopods, Monogena)

Eyes
----Cloudy (bacteria, toxins, poor water quality)
----Red, bloody (bacteria, toxins)
----Dark spots in eyes (embedded parasites, tumors)
----Eyes protruding or pop-eye (exophthalmos) (gas bubble disease, lymphocystis or parasites or tumor
      behind eye in socket pushing eye out, bacteria)
----Eyes sunken (starved, bacteria, Mycobacterium)

Opercules
----Flared (gill parasites, gill infection, toxin damage to gills, large isopod on gills)
----Gasping, irregular opercular beat, rapid opercular beat (bacteria, dinoflagellates, parasites, toxins)

Gills
----Pale gill color (viral or bacterial infection, parasites, toxins, internal bleeding)
----Spots on gills (lymphocystis, bacteria, parasites, dinoflagellates)
----Gill lamellae/filaments fused (bacteria, lymphocystis, hyperplasia)
----Gill lamellae/filaments eroded (bacteria, lymphocystis, parasites)

Color
----Silver or gray or white sheen on skin (bacteria, Mycobacterium)
----Color changes, either getting lighter or darker (virus, bacteria, parasites, toxins)

Growths
----Filaments, nodules, growths, hyperplasia, etc on skin/fins (lymphocystis, tumors, bacteria, fungus,
      parasites, irritants, toxins)

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