🐠 Stuff Every Fish Owner Should Know: Training Guide

Goldfish are big fish with long lives

A well cared for goldfish can live 30 years or more. A child who gets one may still need an adult plan for its care decades later. Goldfish are not short term pets.

Goldfish can grow nearly 23 inches long and weigh 6 pounds or more. The fish may be small at the store but it will not stay small. Plan the tank for adult size, not store size.

A small tank does not set a healthy maximum size for a goldfish. Larger fish need larger tanks to reach full size. A larger water volume also dilutes fish waste and helps keep water quality steady.

Goldfish should not be treated as disposable pets. They need committed care for many years. The family should have a long term care plan before bringing one home.

Bettas are tropical fish with special needs

Bettas are tropical fish. Their water should stay between 76 and 81 degrees Fahrenheit. Most homes are cooler, so an in tank heater and a thermometer are needed.

A betta should ideally live in a 5 gallon tank or larger. More water lets it swim normally and slows the buildup of toxins. Decorations should never crowd a betta to the edges of its tank.

Small bowls are too small for normal swimming and hiding. A small container needs very frequent water changes. A larger filtered tank is better for long term health.

Bettas are carnivores. They eat insects and larvae, not plant roots. They need a balanced pellet or flake food, even if plants are in the tank.

Bettas have a labyrinth organ above the gills. This organ lets them gulp air at the surface. They need easy access to the surface because of this breathing method.

A betta needs good water quality, good nutrition and disease prevention for long term health. Proper diagnosis may require a fish veterinarian.

Match fish and do your homework

Before buying any fish, research the species needs. Fish differ in water temperature, pH and temper. Some fish may attack or eat tankmates.

Goldfish can be a poor match for many tropical fish because their temperature needs differ. Goldfish do best around 65 to 75 degrees Fahrenheit while tropical fish need water near 77 degrees. Research every species before mixing.

Two male bettas cannot share a tank. Adult males can fight and injure each other. Female bettas can be raised in communal tanks.

If you want to add snails or shrimp to a betta tank, the tank and filter must get bigger. Each extra animal adds waste. Bettas are unlikely to get lonely, so tank mates are optional.

Aggression toward newly added fish is common among cichlids and other freshwater fish over about 3 inches long. These fish need enough room for each fish to have its own territory.

Tiger barbs are fin nippers and should not live with angelfish. Different species have different temperaments, so check before you put them together.

Pick a healthy fish and bring it home

A healthy fish has clear eyes, smooth fins and scales, and normal swimming. Cloudy eyes, torn fins, or odd movements like circling can mean trouble. Also look at the fish in the same store tank; if they seem unwell, that is a warning.

An 8 year old cannot be solely responsible for an aquarium. An adult must share responsibility for feeding, testing, cleaning and backup care. Aquarium work can teach planning and responsibility.

Tropical fish in a large aquarium usually cost more to start than goldfish. Bigger setups cost more. Plan your budget before you buy.

Float a new fish bag in the aquarium before release to equalize bag and tank temperatures. Adding fish without this can cause shock and stress.

Keep the water from the transport bag out of your aquarium. Bag water may contain germs.

While a new fish bag floats, rearrange the tank decorations. This breaks up established territorial markers and may calm tankmates.

Place the tank and fill it safely

Keep tanks out of direct sunlight. Sun feeds algae and can warm the water. Warm water holds less oxygen, so choose a spot that is easy to reach for feeding and cleaning.

Water weighs about 8.3 pounds per gallon. A 10 gallon goldfish setup with gravel weighs almost 100 pounds. The floor and stand must be strong, level and stable before you fill it.

Put a cover on the tank to keep fish from jumping out. Do not completely seal the tank because air exchange is important for fish and water quality.

Turn on the filter, heater and pump only after the tank is filled with water. Many aquarium electronics need water to keep them cool and running safely.

How many fish can a tank hold

A common freshwater guideline is 1 inch of adult fish for every 12 square inches of water surface area. Count adult size, not store size.

In a cold goldfish tank, stock fewer fish than in a warm tropical tank. The helpful bacteria that clean waste work more slowly in cold water.

A saltwater tank holds fewer fish than a freshwater tank of the same size. Saltwater carries less dissolved oxygen, and saltwater fish are more sensitive to crowding.

A larger water volume dilutes fish waste and helps maintain water quality.

Start the nitrogen cycle before fish arrive

Before fish enter a new aquarium, set up the tank and verify water quality. Clear water does not prove safe chemistry. Beneficial bacteria usually take 4 to 6 weeks to develop.

Cycling means growing nitrifying bacteria. These bacteria convert toxic ammonia and nitrite into safer nitrate.

Fishless cycling adds an ammonia source instead of fish. You test until ammonia and nitrite both read zero, then fish can be added safely.

Fish in cycling requires frequent testing and small water changes. It can be inhumane if not done carefully because fish are exposed to toxins.

New tank syndrome is caused by ammonia and nitrite spikes. A new filter has not grown enough nitrifying bacteria, and waste quickly builds toxins.

A new aquarium nitrogen cycle can take several weeks to two months. The cycle is done when ammonia and nitrite have peaked and dropped, and nitrate starts to rise.

Stock a brand new aquarium slowly. Add 1 or 2 fish at a time over several weeks, or watch ammonia and nitrite closely, so filter bacteria can keep up.

Ammonia, nitrite and nitrate

Beneficial bacteria turn ammonia into nitrite first. Another group later turns nitrite into nitrate.

The second group of nitrifying bacteria turns nitrite into nitrate. Nitrate is far less toxic than ammonia or nitrite.

Nitrate is the least toxic of the three nitrogen wastes, but high levels still stress fish.

Un-ionized ammonia is about 100 times more toxic than ammonium. Its share of total ammonia rises as pH and temperature rise. Ammonia has no color and no smell, so only a test can find it.

Nitrite is dangerous because it stops blood from carrying oxygen. Fish gills can turn chocolate brown, and fish gasp at the surface.

In a cycled aquarium, ammonia and nitrite should both read zero parts per million. Any measurable ammonia or nitrite can harm fish.

Even a starved fish makes some ammonia. Digesting food is the main source, and more food means more ammonia. Most of a fish ammonia leaves through its gills.

pH, temperature and buffering

Fish are cold blooded. They do not hold a steady body temperature, so the water sets it. This is why the right temperature for each species matters so much.

pH measures how acidic or alkaline water is. The scale goes from 0 to 14, with 7 neutral, below 7 acidic, and above 7 alkaline.

For many freshwater fish, the deadly pH limits are about 4 on the acid side and 10 on the alkaline side. Saltwater fish are much fussier.

A rapid pH drop is more dangerous than a slow change. When pH falls slowly, fish often adapt, but a rapid fall can kill them.

Most tropical fish prefer a stable temperature. Fluctuating temperature stresses fish and weakens immunity.

Tropical aquarium fish need water kept near 77 degrees Fahrenheit. Most homes are cooler than that, so tropical tanks need a heater.

In an established aquarium, pH often slowly drops between water changes because biological filtration produces acid. Regular water changes add buffering and remove acids.

Test, dechlorinate and change water

During a new tank cycle, the most important tests are ammonia and nitrite. Nitrate is useful to watch later.

Most aquarium ammonia test kits measure total ammonia nitrogen, or TAN. To know how much is the toxic form, you also need pH and temperature.

Add dechlorinator to tap water to remove chlorine and chloramines. Dechlorinator makes the water safe for fish and filter bacteria.

Many cities treat tap water with chloramine, a mix of chlorine and ammonia. Both chlorine and chloramine are toxic to fish and helpful bacteria.

Nitrate is removed or reduced mainly by regular partial water changes. Aquarium filters usually do not remove nitrate.

A common weekly partial water change is about 10 to 20 percent. Small bowls without filters need changes more often.

Avoid replacing all the tank water at once. Sudden changes in temperature and pH can shock the fish.

If a tank test shows ammonia, the first thing to do is reduce or stop feeding. A 25 to 50 percent water change also helps remove ammonia if the new water has none.

Private well water usually has no chlorine or chloramine, but it may need aeration. Some deep wells are low in oxygen or carry gases.

Before pouring new water into the tank during a water change, check its temperature. Fast changes in temperature, pH and hardness can stress fish.

Three kinds of filtration

Mechanical filtration traps solid particles. Filter pads or sponges strain particles from the water and keep it clear.

In an under gravel filter, the gravel itself acts as the filter. Water is pulled down through the gravel, which traps particles and grows helpful bacteria.

Chemical filtration often uses activated carbon. It adsorbs some dissolved organic compounds, odors and discoloration. It does not replace biological filtration.

Biological filtration is the work of nitrifying bacteria. They live in the filter and convert toxic ammonia and nitrite into safer nitrate.

Heat, temperature and air

Goldfish and other temperate or coldwater fish usually do not need a heater. Room temperature is fine for them. Tropical fish are different and need a heater.

Bettas are tropical fish and need water between 76 and 81 degrees Fahrenheit. Most homes are cooler, so an in tank heater and thermometer are needed.

Every heated aquarium needs a thermometer to verify the heater. Heater dials can be inaccurate or fail.

A cover keeps fish from jumping out. It should not completely seal the tank because air exchange is important.

Bettas have long, delicate fins and prefer calm water. A low flow, gentle filter is best for them because strong flow can injure fins and cause stress.

Keep the filter bacteria alive

If the filter stops for many hours, beneficial bacteria can die. A dead biofilter lets ammonia and nitrite rise.

Rinse mechanical filter media in dechlorinated water or old tank water. Chlorine in city tap water kills the helpful filter bacteria.

Chlorine and chloramine in city water are toxic to fish and to the helpful bacteria. Always treat new water before it touches the filter.

Nitrifying bacteria need oxygen and water passing over them. Keeping the water surface moving helps oxygen get into the water.

Daily and weekly routines

Make a daily habit of observing your fish, checking the water temperature and equipment, feeding, and clearing away leftover food. A quick check each day catches problems early because fish cannot tell you when something is wrong.

Each week, add water to replace what evaporated, remove algae from the glass, and clean the cover. A tank is a steady chore list, not a one time setup.

A common weekly partial water change is about 10 to 20 percent. Small bowls and betta tanks without filters need more frequent, larger water changes.

A saltwater reef tank with live corals needs much more upkeep than a goldfish setup. Saltwater tanks need more maintenance than freshwater tanks. Choose a setup that fits your available time.

Remove uneaten food after feeding. Leftover food decays into ammonia and can foul the tank.

Feed the right amount

Feed small amounts. Fish should finish everything in about 5 minutes. Goldfish need feeding only once a day.

Overfeeding worsens water quality because uneaten food decays into ammonia. This can overwhelm the biological filter and spike ammonia.

One feeding schedule does not work for every kind of aquarium fish. Feeding rates vary with species, age, aquarium system and water temperature.

Dried fish food should be kept on hand no more than about 2 months. Buying small amounts often is better than one huge tub. Bottom feeders should not be fed flakes that float on the surface.

If you will be away for several days, ask a friend to feed the fish and tell them exactly how much, or simply do not feed until you get back. Dumping in extra food fouls the water. Goldfish can go about 7 to 10 days without food.

Cooler water means a goldfish eats less. Fish are cold blooded, so water temperature sets how much food they need. Goldfish feed actively when water is between 68 and 74 degrees Fahrenheit.

If someone else will feed your fish while you are away, leave clear written instructions. This helps prevent overfeeding.

Safe water changes and cleaning

Avoid replacing all the tank water at once. Sudden changes can shock the fish. Check the new water temperature and add dechlorinator before it goes in.

Never use soap or detergent to clean aquarium gear that goes back in the tank. Rinse tanks, gravel and decorations with plain water and scrub with a brush or cloth.

Before pouring new water into the tank, check its temperature. Fast changes in temperature, pH and hardness can stress fish and make them sick.

Do not leave aquarium lights on 24 hours a day. Fish need a day and night cycle. Constant light stresses fish and may cause algae problems.

Green algae on the glass is caused by too much light. Remove the algae and reduce the light. Live plants help limit algae by soaking up nutrients.

A fish depends completely on you for food and living conditions. Regular care keeps those conditions safe.

Spot disease early

A fish that hides, lies on the bottom or holds its fins tight against its body may be sick. Watching behavior daily helps you catch problems early.

A fish swimming near the surface trying to gulp air is called piping. Rapid breathing and rubbing against objects are warning signs.

Ragged, frayed fins may be a sign of a possible bacterial infection. Ulcers and swelling are other signs. Outbreaks are often tied to poor water quality and stress.

Grayish white cotton like growths on a fish may be a fungus called Saprolegnia. Some bacteria can also look cotton like, so a fuzzy look alone does not prove the cause.

Tiny white dots like grains of salt on fins are a likely sign of ich, a skin parasite. Other diseases can look similar, so white spots alone should not be the only diagnosis.

Even a low level of ammonia stresses fish and damages gills and other tissues over time. Fish exposed to ammonia get more bacterial infections and grow poorly.

Dropsy describes fluid building up in the abdomen. It can appear with bacterial disorders, so a veterinarian or fish health professional should diagnose the cause.

Quarantine and fish veterinarians

Quarantine valuable pet fish for 30 to 60 days before they join the established population. This helps prevent a newcomer from spreading disease.

Once quarantine starts, adding another new fish restarts the quarantine clock. Each newcomer could bring its own germs.

Hold new live plants with no fish for one ich life cycle. Ich can hitch a ride on plants, gravel and equipment, not just fish.

A sick fish can be watched and treated more easily in a separate quarantine tank. This also helps keep disease away from other fish.

Use separate nets and siphon hoses only for the quarantine tank. A wet net dipped from tank to tank can carry germs.

A simple low cost home quarantine tank can be a 10 gallon tank with a sponge filter, air pump and heater. It does not need to be fancy.

Some veterinarians treat pet fish. Treatments such as injections or surgery require a veterinarian. Emergency fish care is less available than dog and cat care.

Vaccines are still uncommon for pet aquarium fish. Pet fish health depends more on water quality, good food, cleaning and quarantine.

Ich treatment must be repeated because one dose misses parasites that hatch later. Treatments are timed by water temperature because the life cycle runs faster in warm water.

Protect yourself and never release fish

Mycobacterium germs can cause fish tank granuloma in people. It shows up as sores or bumps, usually on the hands, and can enter through skin cuts from fish or tank water.

A fish that looks perfectly healthy can still spread germs like Salmonella to people. Just because a fish looks healthy does not mean it is germ-free.

Before changing water, unplug the filter, light and air pump. Water and electricity do not mix. Only plug things in with dry hands, and kids should do this with an adult.

Be careful with sunscreen, perfume and bug spray near your aquarium. These chemicals can harm fish. Rinse your hands and keep sprays away.

Do not release pet fish into a pond or river. Most will die, and some can threaten native wildlife.

A good way to rehome a fish is to give it to another fish hobbyist, or ask a local aquarium, school or zoo to take it. Ask a store about returns or surrender events.

Get rid of unwanted aquarium plants by sealing them in a plastic bag in the trash. Do not compost them because seeds and plant pieces may spread.

In Minnesota, releasing a pet goldfish into a lake or pond is illegal. Goldfish are classified as a regulated invasive species there.

Power outages and emergencies

Most home aquarium emergencies are not truly medical. They usually involve equipment or water problems, like a leak or a broken heater or pump.

If a storm may knock out your power soon, stop feeding a day or two early. Less food means less waste, and the filter may stop working.

When the power goes out, keep the water surface moving. Oxygen dissolves into water at the surface, and a battery air pump keeps it moving.

After power returns, wait 24 hours before feeding. Test the water for ammonia and nitrite, and clean filters before plugging them back in.

During a summer outage, if the tank gets too warm, blow a battery fan over the open top. Cool slowly, about 1 to 2 degrees Fahrenheit every few hours.

In a long outage, keep filter bacteria alive by putting the filter media in an aerated tank or container. Put it back when power returns.

Keep at least 10 to 20 percent of the tank volume in treated water for emergencies. Also keep dechlorinator on hand.