Beginner aquarium guides

53 guides, in the order a first tank needs them. Each one answers one question and commits to the answer.

Maintenance

Water changes, cleaning, algae, snails and smells. 17 guides.

Maintenance12 min
How to Get Rid of Duckweed in an Aquarium Without Hurting Fish
How to get rid of duckweed in an aquarium without hurting fish: net it, wipe the glass, pick it out of moss, then check for six weeks so it stays gone.
Maintenance11 min
How to Tell If a Mystery Snail Is Dead: A 3-Step Check
How to tell if a mystery snail is dead: check its grip, its trapdoor, then the smell. Floating is not a sign. Then head off the ammonia spike.
Maintenance4 min
Biofilm in an Aquarium: The Slime You Mostly Want, and the Film You Don't
Biofilm is the thin layer of bacteria on every surface in a tank, and most of it is useful. When surface film or slime is a problem, and how to fix it.
Maintenance4 min
Black Algae in a Fish Tank: Black Beard Algae and How to Remove It
Black algae in a fish tank is almost always black beard algae: dark tufts on leaf edges and wood that will not wipe off. Why it grows and how to get rid of it.
Maintenance4 min
Blue-Green Algae in an Aquarium: It's Bacteria, and How to Clear It
Blue-green algae is cyanobacteria: a slimy sheet that peels off and smells like a swamp. Why it grows, how to remove it, and how to keep it from coming back.
Maintenance3 min
White Algae in a Fish Tank: What the White Stuff Actually Is
White fuzz, film or crust in a fish tank is rarely algae. Most often it is harmless growth on new driftwood or mineral deposits. How to tell which one you have.
Maintenance7 min
Brown Algae in Fish Tank: Why It Happens and When It Ends
Brown algae in fish tank? It is almost always diatoms. How to confirm it, how long a new-tank bloom lasts, and what actually clears it.
Maintenance4 min
How to Get Rid of Snails in an Aquarium, Without Chemicals
How to get rid of snails in an aquarium: feed less, trap them overnight, and add assassin snails if you keep no snails you want. Skip the chemicals.
Maintenance3 min
Hydra in an Aquarium: Harmless to Fish, Deadly to Fry
Hydra in an aquarium look like tiny stalks with tentacles. They are harmless to adult fish but eat fry and baby shrimp. How to starve them out or treat them.
Maintenance3 min
Planaria in an Aquarium: Harmless to Fish, Bad for Shrimp
Planaria in an aquarium are flatworms that glide on the glass. With fish they are harmless. In a shrimp tank, here is how to trap them and treat safely.
Maintenance4 min
Worms in a Fish Tank: Which One Is It, and Does It Matter?
Worms in a fish tank are usually harmless detritus worms. Identify yours in one table, and learn the two that need action: planaria and camallanus.
Maintenance5 min
How to Change Fish Tank Water, and How Often to Do It
How to change fish tank water: replace 25% once a week, with new water dechlorinated and matched to within 2°F. The steps, and how to set your own schedule.
Maintenance5 min
Scuds in an Aquarium: Harmless With Fish, a Problem With Shrimp
Scuds in an aquarium are tiny curled crustaceans that swim on their side. With fish they are free live food. With only shrimp they are a rival.
Maintenance4 min
Snail Eggs in a Fish Tank: Which Snail, and Will They Hatch?
Snail eggs in a fish tank look different for every species. Identify yours in one table — clear jelly, pink clutch or hard white dots — and if they will hatch.
Maintenance4 min
Why Does My Fish Tank Smell? Match the Smell to the Cause
Why does my fish tank smell? A healthy tank smells like damp soil. Rotten eggs, rotting fish and musty swamp each point to one cause — matched in one table.
Maintenance3 min
Detritus Worms in a Fish Tank: Harmless, But Check First
Detritus worms in a fish tank are harmless waste eaters. A sudden bloom means overfeeding — and here is how to tell them apart from planaria, which are not.
Maintenance3 min
How to Clean Aquarium Decorations Without Killing Fish
How to clean aquarium decorations: hot water and a toothbrush for most of it, a 1:9 bleach soak for stubborn algae, then rinse and dechlorinate. Never soap.

What you'll find here

These guides follow the order you actually need them in: choosing a tank and working out what it really costs, the equipment that matters (filter, heater, light, substrate) and what you can skip, the nitrogen cycle and how to run a fishless cycle properly, then stocking (beginner-friendly fish, easy live plants) and the maintenance routine that keeps it all stable.

Every guide is written by a named human author who keeps tanks, gives you the numbers to test against rather than vague advice, and gets updated when better information turns up. Read more about our editorial standards.

Maintenance

How to Get Rid of Duckweed in an Aquarium Without Hurting Fish

How to Tell If a Mystery Snail Is Dead: A 3-Step Check

Biofilm in an Aquarium: The Slime You Mostly Want, and the Film You Don't

Black Algae in a Fish Tank: Black Beard Algae and How to Remove It

Blue-Green Algae in an Aquarium: It's Bacteria, and How to Clear It

White Algae in a Fish Tank: What the White Stuff Actually Is

Brown Algae in Fish Tank: Why It Happens and When It Ends

How to Get Rid of Snails in an Aquarium, Without Chemicals

Hydra in an Aquarium: Harmless to Fish, Deadly to Fry

Planaria in an Aquarium: Harmless to Fish, Bad for Shrimp

Worms in a Fish Tank: Which One Is It, and Does It Matter?

How to Change Fish Tank Water, and How Often to Do It

Scuds in an Aquarium: Harmless With Fish, a Problem With Shrimp

Snail Eggs in a Fish Tank: Which Snail, and Will They Hatch?

Why Does My Fish Tank Smell? Match the Smell to the Cause

Detritus Worms in a Fish Tank: Harmless, But Check First

How to Clean Aquarium Decorations Without Killing Fish

What you'll find here