Aquarium Fish FAQ

The best beginner fish are hardy and forgiving of water quality fluctuations:

• Betta fish — Perfect for small tanks, beautiful, easy to care for
• Guppies — Colorful, hardy, breed easily
• Platies — Hardy, peaceful, many color varieties
• Mollies — Adaptable, peaceful community fish
• Zebra Danios — Extremely hardy, active swimmers

Take our quiz → to find your perfect fish.

Cycling establishes beneficial bacteria that convert toxic ammonia (from fish waste) into less harmful nitrates. Here's how:

1. Set up your tank with filter, heater, and dechlorinated water
2. Add an ammonia source (fish food or pure ammonia)
3. Test water daily with a kit (API Master Test Kit is recommended)
4. Wait 4-6 weeks — ammonia will spike, then nitrite, then both drop to 0
5. When ammonia = 0, nitrite = 0, and nitrate is present, you're cycled!

Never add fish to an uncycled tank. Ammonia poisoning is the #1 killer of new fish.

The old "1 inch of fish per gallon" rule is a rough starting point, but it's oversimplified. Consider:

• Adult size — Use the fish's full-grown size, not current size
• Activity level — Active swimmers need more space
• Bioload — Messy fish (goldfish, plecos) need more filtration
• Territorial needs — Some fish need their own space

Example stocking for a 10-gallon tank:

• 1 Betta (alone or with snails/shrimp)
• OR 6-8 Neon Tetras + 3-4 Corydoras
• OR 6 Guppies + 1 Mystery Snail

Weekly 20-30% water changes are the foundation of good fish keeping.

• Removes nitrates that build up over time
• Replenishes minerals fish need
• Use a gravel vacuum to clean the substrate
• Always treat new water with dechlorinator
• Match the temperature of new water to tank water

Consistency is key — regular small changes are better than occasional large ones.

Cloudy water has different causes:

• White/gray cloudy — Bacterial bloom, common in new tanks. Usually clears in a week.
• Green cloudy — Algae bloom. Too much light or nutrients. Reduce lighting, do water changes.
• After water change — Stirred up debris. Should settle within hours.

Solutions:

• Don't overfeed (most common cause)
• Ensure adequate filtration
• Do regular water changes
• Be patient — new tank cloudiness often resolves itself

Choose a filter rated for at least your tank size, ideally 1.5-2x larger.

• 20-gallon tank → filter rated for 30-40 gallons
• Look for filters with good biological filtration (where bacteria live)
• HOB (hang-on-back), sponge, or canister filters are all good options
• More filtration is almost always better

For Bettas and other slow swimmers, choose filters with adjustable flow to avoid strong currents.

Once or twice daily, only what they can eat in 2-3 minutes.

• Overfeeding is the #1 mistake beginners make
• Uneaten food rots and pollutes the water
• Fish stomachs are tiny — a few flakes/pellets is plenty
• Skipping one day a week is actually good for their digestion
• Vary their diet with flakes, pellets, and occasional frozen foods

Remember: A hungry fish is a healthy fish. They always look hungry!

Most tropical fish thrive at 75-80°F (24-27°C), but it varies:

• Bettas: 78-82°F — prefer warmer water
• Neon Tetras: 72-78°F — mid-range tropical
• Zebra Danios: 64-77°F — tolerate cooler temps
• Oscars: 74-81°F — warm water cichlids

When keeping multiple species, find their overlapping temperature range. Use a reliable heater with a thermostat.

Yes, for almost all tropical fish.

• Most tropical fish need stable temps of 75-82°F
• Room temperature fluctuates, especially at night
• Temperature swings stress fish and weaken immune systems
• Get a heater rated for your tank size (usually 3-5 watts per gallon)
• Use a separate thermometer to verify temperature

Exceptions: Some fish like White Cloud Minnows and Goldfish prefer cooler water and don't need heaters.

Yes, but choose carefully! Consider:

• Temperament — Don't mix aggressive with peaceful
• Size — Big fish may eat small fish
• Water parameters — pH and temperature preferences should overlap
• Swimming level — Mix top, mid, and bottom dwellers for visual interest

Safe community fish: Tetras, rasboras, corydoras, livebearers, and peaceful gouramis.

Use our Compatibility Checker →

Male Bettas must never be kept with other male Bettas. However, some can live with peaceful tankmates:

Often compatible:

• Corydoras catfish — bottom dwellers, ignored by bettas
• Mystery snails — peaceful cleanup crew
• Cherry shrimp — may be eaten, but often coexist

Avoid: Guppies (colorful = target), fin nippers, other labyrinth fish

Success depends on individual betta personality and a large enough tank (10+ gallons recommended).

Test your water first! Most fish deaths are caused by water quality issues.

Common causes:

• Ammonia/nitrite poisoning — Tank not cycled or overstocked
• Temperature shock — Sudden temperature changes
• Chlorine — Forgot to dechlorinate new water
• Incompatible tankmates — Aggression or stress
• Overfeeding — Pollutes water and causes bloat
• Disease — Often caused by stress from above factors

Healthy water parameters: Ammonia 0, Nitrite 0, Nitrate <40ppm, pH stable for your species.

Lifespan varies greatly by species:

• Bettas: 3-5 years
• Guppies: 2-3 years
• Neon Tetras: 5-8 years
• Corydoras: 5-10 years
• Angelfish: 10-15 years
• Oscars: 10-20 years
• Plecos: 10-15+ years

Proper care significantly impacts longevity. Fish often die young due to poor water quality, not old age.