Aquarium Problems
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Aquarium and Fish Problems





Small white spots on fins. Eventually the spots will cover much of the body. Fish will scratch and become listless

Ich is a common parasite of fish. When fish are chilled or moved they become more susceptible. Ich is easy to cure if you treat daily for at least 3 days. Use Quick Cure or similar. To speed the cure raise the temperature to 80 degrees.


There are a number of external parasites which may attack the skin, gills, and fins of the fish. Fish which are infected with external parasites will begin to act differently, and may scratch against rocks, or hover near the bottom of the tank. You can suspect a parasite problem if you see any of the following symptoms:
White Spots
Excessive Gill Movement
Red Streaks
Excessive Hiding
White Film

Raise temperature to 80 degrees, Do a partial water change. Add one of the following:
Nox Ich,            Goldfix,                  General Cure
Maracide,      CopperSafe,  Quick Cure
Lifeguard Super Ich Cure

Notes: The most common parasite of fish is Ich which is highly contagious and causes white spots about the size of a grain of salt to appear on the fins and body. Treat immediately. Treat for at least 3 consecutive days. Repeat if needed.

Cloudy Water

* Water is cloudy or hazy
* White mold-like growths on rocks, plants
* " Gooey" pieces of debris cling to gravel
* Fish become listless, increased chance of fin rot

Cause: This is the most common problem experienced by beginners. It is usually due to:
1. Overfeeding: We have found that over 80% of cases of cloudy water are due to overfeeding. Decaying food creates a bacterial bloom and clouds the water.
2. New Tank: Cloudy water often occurs for a few days after you first set-up a tank. Maintain normal filtration and the tank will clear on its own. " Brite and Clear" , or " Filter Aid"   tonic will speed the clearing.

Treatment: Do a partial water change of 25%. Review feeding procedures.
Maintain adequate filtration, and use fresh activated carbon in the filter.
Add " Brite and Clear" tonic.

Poor Water Quality

Loss of color (majority of fish)
Excessive hiding
Red streaks
Unusual darting about
Fin rot listlessness
Cloudy eye white film

Often several fish die rapidly

Cause: The most common cause of water quality problems is the buildup of ammonia due to decaying food, overcrowding, or inadequate biological filtration. Ammonia problems also will occur in newly set-up tanks (during the first 3-4 weeks) if you add to many fish before your biological filter is fully operating.
Other causes of water problems include inadequate filtration, improper pH, insufficient aeration, and contamination from paints, sprays, insecticides, or cleansers.

Treatment: If you suspect a problem with the water quality first test the pH and ammonia level of your tank.
* If ammonia level is high (above 1 ppm.)
* If pH is too acid:
In all other cases do a partial water change by siphoning 25% of the water from the bottom of the tank. Repeat the partial water change daily until the problem clears. Also check the operation of your filters, and add fresh activated carbon to the filter.
Poor water quality can weaken the fish and make them susceptible to bacterial infections.
Therefore we often recommend an antibiotic as part of the treatment.

Notes: If nearly all of the fish die over a very short period of time it is usually because of a build-up of a toxin in the water. An infectious disease can usually be ruled out because they take several days to progress.

Bacterial Infections

You can suspect a bacterial infection if you see any of the following symptoms:

Fin Rot Excessive Gill Movement
Red Streaks Excessive Hiding
White Film Listlessness
Open Sores Cloudy Eye
Sunken Belly, Bulging Eye (Popeye),
Mouth Fungus (Contagious)

Notes: Most fish have a good natural resistance to bacterial infections, and a healthy fish will often be able to resist an infection on its own. For this reason not all bacterial infections are contagious. Often only the weaker, older, and most susceptible fish will succumb. The best way to prevent bacterial infections is to feed the fish quality FRESH foods, and maintain a healthy environment so that their natural resistance will help them fight the infection.
Treatment: Raise temperature to 80 degrees, Do a partial water change. Add one of the following antibiotics:
* Maracyn (Fin rot, white growths)
* Maracyn II (Eye cloud, sores, red streaks, popeye,
bloat, fin rot)
* Furan-2 (Mouth fungus, fin rot, sores)
* Tetracycline (Hospital tanks, use for serious infections: will discolor water and clear Silicon)
* Jungle Fungus Eliminator
If no response is seen within 4 days, switch to a different medication. Bacterial infections are often associated with external parasites, and a combination treatment for parasites is usually advisable.


White Fuzzy Growths on fish

Do a partial water change. Add one of the following:
Fungus Cure
MarOxy (also prevents fungus on eggs)
Nox Ich (has limited affect on fungus)

Notes: Usually affects only weak or injured fish. Not usually contagious.

Cloudy Eye

White film on eye

Can be caused by several factors. Often it is due to a reaction to something in water such as low pH, medication overdose, or poor water quality. Overcrowding, bacterial infections, internal infections, nutritional deficiencies, and old age can also be factors. Treatment: do a 25% water change and check pH. Repeat water change in two days.
Add Maracyn II.

Inadequate Diet

Fish gradually becomes thin, loss of color, sunken eyes, emaciated stomach, in later stages fish will lie on bottom and may develop sores.

This is a bacterial infection that usually only affects one or two fish at a time and progresses slowly over a period of several months. If you are certain the problem is not due to inadequate diet isolate the infected fish in a separate tank or fish bowl. Treatment is not always effective, but feed them medicated food exclusively for several weeks. If problem persists over a period of several months clean and disinfect the tank.

Black Molly Disease

White patches on body of black mollies

This is not a specific disease, but we receive a lot of calls about mollies. Mollies are more prone to skin infections than many other fish. It is not contagious, but can be treated with MarOxy. Also keep them warm (78-82 degrees) and keep at least one teaspoon of salt per 5 gallons.

Lack of Oxygen

Fish gasp at surface, death occurs with mouth wide open

Increase aeration check filter system. Do not overcrowd. This usually does not occur in filtered aquariums, but is a common problem in goldfish bowls.


Fish dash wildly about, they may also simply hover near the surface or remain near the bottom.

Shock is caused by making an environmental change (such as water change or temperature change) too quickly. Make any change to the fishes environment gradually.

Incompatible Tank Mates

Fish hides in corner, and in some cases it may hover in a head down position. Fins may appear ragged and scales may be missing.

Keep only fish of similar size together. Provide adequate hiding spots and feed properly. Check with store personnel regarding species compatibility recommendations. In some cases the " bully" fish must be separated from the weaker fish. Large fish can sometimes be brought into the store for partial credit towards some other fish.

Problems with Newly Purchased Fish

Newly purchased fish do not adapt well to the tank. In some cases they will hide and will not eat, or hover near the surface. Loss of one or more fish occurs within a few days of purchase.

When a fish is transferred from one tank to another, there is a certain amount of stress involved and some fish may not be able to adapt. The loss of one or two fish out of a group is not normal, but if it occurs it does not necessarily indicate a serious problem.
Keep a close eye on the other fish for a few days. If you are having problems with new fish, we also suggest that only the more hardy fish be purchased for a while.
Check store guarantee policy for replacement.

One fish dies in a healthy tank

One fish dies showing no symptoms. All other fish remain healthy

It is often difficult to pinpoint the cause of a problem when only one fish is affected, particularly if it showed no symptoms before death. The cause can be any of a number of factors including an internal infection, worms, bacterial infection, malnutrition, injury, or old age. In most cases there is nothing special that should be done. Keep a close eye on the other fish and if they begin to show any symptoms of disease do a partial water change and treat accordingly. Most of the time it will not be contagious.

Old Age

Fish becomes listless, lies on bottom, hover near top, sometimes belly becomes very thin, and bent spine occurs.

As a general rule, the smaller fish such as tetras, mollies, guppies, neons, swordtails, will live no more than 3 years. Some of the larger fish such as cichlids, angels, goldfish, can live 5 years or more.


White fuzzy growths, on rocks, plants, gravel. Sometimes forms white balls.

This is a mold that grows on extra fish food. See above: "Cloudy Water."

Green Algae

Green growths on glass, gravel, plants, wood, or ornaments

Excessive amount of green algae is usually caused by too much light Avoid direct sunlight, leave the aquarium light on no more than 8 hours a day. Add some algae eating fish (plecostomus, true siamese algae eaters). Scrape sides of tank with algae scraper. Add an algacide to prevent new growth. Add a background to shade tank from sunlight.

Unwanted " little bugs"

Tiny organisms are seen in tank

There are many small organisms which occasionally become established in an aquarium. Fortunately most are not harmful. They are often introduced with live plants. These organisms can include tiny worms, planaria, leeches, and crustaceans. Keep the bottom free of extra food and you will be able to control their growth rate. Sometimes copper sulphate solution or " Clout" will kill them, but use with extreme caution. Corydoras catfish also help to keep small organisms from growing in the tank.

Unwanted Snails

Snails multiply very quickly

Limit the snails growth rate by keeping the aquarium bottom free of extra food or plant leaves. Use any chemicals VERY carefully and do not overdose. The large snails such as Mystery snails, Gold snails, and Nerite snails do not create this problem.

Power Failure

Filtration shuts down due to power failure. Hurricane anyone?

In a normally stocked aquarium fish can survive for a long time without power or food, but not without aeration. The time will be less for crowded tanks and more for un-crowded tanks. If the fish begin to come to the surface, oxygen depletion is indicated.

Begin preperation early (before  the storm):

  1. Lower tank temp to mid-70's, NOW! But VERY Slowly if you can. At reason ably lower temperatures, water will hold more oxygen. If the power is already out, let it adjust on its own.
  2. Change the water, NOW! The lower organic and nitrogen levels will buy more time for the animals. Again if organics are low, water holds more oxygen.
  3. Change the filter materials, NOW! Again, this will remove organics and pollutants to give the fish more time. If you have a protein skimmer, clean it and make sure it is working well, now,  as  well.
  4. Buy and TEST battery operated air pumps, NOW! Larger tanks need more than one. Make sure you have a good supply of the right kind of batteries. Get course air stones, not bubble curtain stones. You need maximum water movement. Do NOT put the air stone on the VERY bottom, it will stir up too many organics.
  5. Remove the glass covers or canopies. This allows for better gas and heat exchange,  especially if you don't have another source of circulation.
  6. Manual agitation of the water surface also helps. In tanks with lower populations this may get you by for days but is can frighten and stress the fish. Get Battery Operated pumps, NOW!
  7. Add a small amount of ammonia reducer to the water every day or so. TEST for ammonia, nitrites, and nitrates. Do NOT let them build up.
  8. Do not feed the fish while the filter is off! There is a much greater chance of  killing  them  with ammonia poisoning than starvation. Fish can almost always go for a week or even two without anything but what is already in the tank growing on plants, the substrate, and the tank walls.

Water too warm in summer

Water temperature rises above 85 degrees.

Temperatures above 85 degrees can subject the fish to stress and even kill them unless they are fish which NEED that kind of heat (rare). Water will hold less oxygen at warmer temperatures than at colder temperatures. Therefore increasing the amount of aeration is often the best procedure when the aquarium becomes too warm. If the temperature goes above 90 degrees, ice cubes inside of plastic bags can be placed in the tank. Consider installing fans or a chiller.

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