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Salmon in the Classroom Resource Menu Bar

Tank Problems

Feeding Problems

Cloudy Water

Dying Fish

Our Fish Are Dying!!!
The Most Common Causes of Fish Death

All Salmon Tanks

1. Dirty Water

Usual Cause: Overcrowding (Bigger fish), under-cleaning (housekeeping), over-feeding, improper feeding (See Feeding for your type of system.).

Diagnosis: pH may be low (below 6.6); ammonia may be present. There may be brown crud on bottom of tank, there may even be mold on the crud. Water may be cloudy and smelly.

Treatment: Clean that tank! In extreme cases, it may be necessary to do a complete gravel wash.

Prognosis: Excellent if you get the water clean and keep it clean. Prevention: Re-read Salmon Tank Time-line and Feeding for your type of system. Follow the instructions exactly. Monitor your water chemistry. Don't overcrowd your tank.

2. Exposure to copper or zinc

NOTE: We humans prepare our food in utensils made of copper and galvinzed metals and it doesn't bother us. Salmon, however, are extremely sensitive to these substances. For more information contact the manager of the Washington State Salmon in the Classroom Program.

Usual Cause: Copper pipes and/or new galvinized pipes containing zinc. Symptoms generally appear shortly after the fish hatch or at swim up.

Diagnosis: Have your water tested at a water quality laboratory. Check your building's pipes; are they copper?

Treatment: Get the fish into better water immediately. Get water from a building which is known to have raised salmon successfully or buy bottled water.

Prognosis: Good if you act fast to get the fish into other water. If your tap water has a zinc or copper level higher than is safe for salmon, you can still raise salmon in your building if you use a ion exchange cartridge to filter the water.

Prevention: See if your building has copper pipes. Have your tap water tested before you begin raising salmon. If necessary, install an ion exchange cartridge. Since the ion exchange cartridge removes calcium also, see the next item 3. Calcium deficency.

3. Calcium deficiency

Usual Cause: Your filter system has removed calcium from water. (Calcium, a metal, is removed by both the Chemipure charcoal for the closed sytem tank and the ion exchange cartridge for the semi-open system tank.) Symptoms generally appear when fish are entering the parr stage.

Diagnosis: Perform chemical test for calcium. Optimum levels are 25-100 mg/l.

Treatment: For a 55-gallon tank, add 8.3 grams of calcium chloride and 7.7 grams of magnesium sulfate (Epsom salt) to the water. We use laboratory grade calcium chloride for this; in an emergency you can get it quickly from a high school chemistry teacher. Epsom salt may be obtained from your local drug store.

Prognosis: Excellent! Even moribund fish revive with astonishing speed.

Prevention: Keep oyster shells in the tank at all times to provide a calcium source to replace the calcium removed by your water filtration systems.

4. Saprolegnia

A fuzzy fungus growing on dead eggs. It can be ignored unless it spreads to healthy eggs.

Usual Cause: Dead eggs not yet removed.

Diagnosis: A fuzzy whitish fungus begins to grow on dead eggs. The fungus generally appears in December or early January and persists until all dead eggs are removed.

Treatment: Remove the dead eggs as soon as the healthy ones have eyed. If there is a lot of fungus and it is spreading over your healthy eggs, you may have to remove the dead eggs before the healthy ones eye, even if it means killing a few healthy ones.

Prognosis: Depends on how much fungus is present and for how long. Healthy eggs not directly in contact with the fungus do not appear to be injured by it. However, if the fungus spreads over healthy eggs, it can thin the shells and cause the fish to hatch prematurely.

Prevention: When you first pour the eggs into your egg tray, try to spread them out so that, if necessary, individual dead eggs can be picked out without jarring healthy eggs. Take out dead eggs as soon as possible after they eye.

5. Premature Hatch

Usual Causes: Saprolegnia. Power outage.

Diagnosis: Fish hatch earlier than you expected. Individual alevin do not have the gold rim around their eyes. They are small, and their bodies have a pale, wispy appearance.

Treatment: Darken the tank as much as possible and leave the fish strictly alone. It is important that these "preemies" use all their energy for growing, not wriggling around the tank getting stressed out. We cover the sides, front, back, and most of the top of the tank with laminated black butcher paper until the babies are larger and have a gold rim around their eyes.

Prognosis: Good if the fish aren't stressed.

Prevention: Do not allow saprolegnia to get out of control. If you have a power outage, your fish will be okay if the water does not get too warm (unlikely if your building's heat is off) or too low in oxygen. Aerate the water with a battery operated airstone during power outages. Battery operated airstones are available at pet stores; we use a brand called PetceteraTM. In a long outage, if your building is very cold, you can drain the water to a level below the egg tray and let the eggs sit in the air. If they are kept cold and damp, the eggs should be okay until the power comes back on.

6. Feeding Problems

Usual cause: Not following directions.

Symptoms: Fish in the same tank vary greatly in size. Skinny fish with large heads (pinheads). Layer of uneaten food on bottom of tank. Cloudy water. Smelly water.

Treatment: Re-read the directions about how to feed the fish properly and follow them exactly. Clean the tank. For pinheads: many of these may be too weak to save; read section on wimps and bullies. (See Feeding for your type of system.)

Prognosis: Proper feeding and care of the tank will save most of your fish if they aren't too weak.

Prevention: Follow feeding instructions. Fish are most vulnerable when they are just learning to eat. Be patient and persistent when tease feeding. (See Feeding for your type of system.)

Open and Semi-open System Tanks

1. Ion Exchange Cartridge Failure

Cause: Ion exchange cartridge has worn out and metals (like copper) that are harmful to fish are getting into the tank.

Symptoms: Fish appear unusually agitated. Alevin may leap up off the bottom and jerk around in an odd way.

Diagnosis: Inspect your cartridge. If it has turned completely yellow, you are overdue to change it. Is your ion exchange cartridge turning yellow at its usual rate? If it has run for many hours but shows no yellow at all, it may be defective. Get a sample of the new water flowing into the tank and do a calcium test. If you detect calcium in the water coming into the tank, you may assume that the ion exchange cartridge is no longer working.

Treatment: Change the cartridge. If you think copper has gotten in the tank, do a 1/3 water change. Wait awhile, then if the fish still appear agitated, do another. Since new water coming in may be low in oxygen, be sure your airstones are running at full power to replenish it as rapidly as possible. New water will certainly be low in calcium so if you have to do a major water change, add 8.3 grams of calcium chloride and 7.7 grams of magnesium sulfate to the tank after you change the water. If the pH is excessively low, add a small amount of baking soda to bring it up to neutral (pH 7.0).

Prognosis: Uncertain. If the fish have not been badly damaged, and if the problem is fixed they may be fine.

Prevention: Monitor your cartridges; become familiar with their wear patterns (Open System and Semi-Open System diagram instructions). Become familiar with fish behavior so that you know when your fish are acting peculiar.

2. Adsorber Cartridge Failure

Cause: Adsorber filter cartridge has worn out and chlorine is getting into the tank.

Symptoms: Fish appear unusually agitated during water change. Alevin may leap up off the bottom and jerk around in an odd way.

Diagnosis: Inspect your cartridges. Is it time to change your Adsorber? Occasionally an Adsorber may be defective or may be "killed" by a big pulse of chlorine sent through the city water system when workmen are repairing water lines near your school.

Treatment: Change your Adsorber cartridge. Mix some Shieldex with a bucket of aquarium water and pour it in your tank to dechlorinate the water.

Prognosis: Uncertain. If the fish have not been badly damaged, and if the problem is fixed they may be fine.

Prevention: Monitor your cartridges. Become familiar with their wear patterns. Use a permanent marking pen to write the date on the Adsorber cartridge when you install it. Remember to put a mark on your Adsorber every time you change the Ion Exchange Cartridge . (See Open System or Semi-Open System diagram) Become familiar with fish behavior so that you know when they are acting peculiar. Avoid running the flow-through on weekends when there is no one around to observe.

Salmon in the Classroom Home Page
Getting Started
Care and
The Field Trip
Closed Tank | Open Tank | Semi-open Tank | The Salmon
Closed Tank Timeline | Open Tank Timeline | Semi-open Tank Timeline
Closed Tank Feeding | Open Tank Feeding | Semi-open Tank Feeding
Planning | Background Info | Worksheets | Leader worksheet key
Tank | Feeding | Cloudy water | Dying fish | Gravel wash
Funding | Permits | Glossary | Locating Special Equipment| Additional Resource 

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