Aquarium guides
Short, practical answers to the questions every fishkeeper asks, checked against reliable sources.
Getting started
Aquarium nitrogen cycle explained, with week-by-week readings
How the aquarium nitrogen cycle turns fish waste into ammonia, then nitrite and nitrate, which microbes do the work, week-by-week readings and when it is done.
How many fish per gallon? Why the 1-inch rule fails
The 1 inch of fish per gallon rule breaks for both tiny and large fish. See a better method, with 3 worked tank examples and real stocking percentages.
How to cycle a fish tank: fishless and fish-in, step by step
How to cycle a fish tank: dose ammonia to 2 ppm, test on a set schedule, speed things up with seeded media, or run a fish-in cycle if fish are already home.
How to set up a fish tank: a 10-step checklist for beginners
How to set up a fish tank step by step: choose the size and spot, size the heater and filter, treat tap water, cycle for 4–8 weeks, then add fish slowly.
Water & maintenance
Ammonia in a fish tank: causes, symptoms and how to fix it
High ammonia in a fish tank? Do these emergency steps first, then find the cause. Safe levels, a pH and temperature toxicity table, symptoms and prevention.
Aquarium water parameters chart: safe ranges for freshwater
Safe ammonia, nitrite, nitrate, pH, GH, KH and temperature levels for freshwater tanks, how to test them, and how to fix each one without shocking your fish.
How much water to change in a fish tank (and how often)
How much water to change in a fish tank: 25–30% a week for most tanks. Gallons by tank size, the nitrate math, a step-by-step method and mistakes to avoid.
How to clean a fish tank without crashing the cycle
A weekly routine to clean a fish tank: glass, gravel vacuum, water change and a filter rinse in tank water, plus which jobs never to do on the same day.
How to get rid of algae in a fish tank: types and fixes
Get rid of algae in a fish tank: identify green dust, black beard, cyanobacteria or green water, then fix the light and nutrient imbalance that feeds it.
What temperature should a fish tank be? Ranges by species
Most tropical tanks belong at 75–80 °F (24–27 °C). See ranges for popular fish, coldwater and warm-water species, heater sizes and summer cooling fixes.
Why is my fish tank cloudy? Causes and fixes by water color
White, green or brown aquarium water each has a different cause. Find yours by color, fix it step by step, and learn when cloudy water is harmless.
Fish care
Best algae eaters by tank size, including betta tanks
The best algae eaters for 5 to 55+ gallon tanks, which algae each one actually eats, safe picks for betta tanks, and the ones that outgrow most aquariums.
Best fish for beginners: hardy picks by tank size
The best fish for beginners, sorted by tank size, with the minimum tank, group size and temperature for each, plus popular fish new keepers should avoid.
How to acclimate fish: float, cup and drip methods step by step
How to acclimate new fish and shrimp safely: when to float, when to drip, why shipping bag water burns gills, quarantine basics, and which fish to add first.
Health
Fin rot in fish: causes, stages and treatment
How to treat fin rot: fix the water first, remove the cause, know when medicine is needed, tell rot from fin nipping and see what healthy regrowth looks like.
How to treat ich (white spot disease): symptoms and treatment
How to treat ich (white spot disease): spot the signs, then use medication, careful heat or salt, with safe options for loaches, catfish, shrimp and snails.
Why are my fish dying? A test-first checklist to find the cause
Fish dying in your tank? Test ammonia, nitrite, nitrate, pH and temperature first, then work through this checklist of causes, fixes and when to see a vet.