For your first 30 days
Keep your first fish alive.
A daily coach for a new tank: what to test, what to do, when to add fish.
The nitrogen cycle in one picture
Why new tanks kill fish, and how long it lasts
AmmoniaNitriteNitrate
Free calculators
Quick answers, with reasons
Sound familiar?
Built for the tank you just set up
“The store sold me fish and a tank on the same day.”
“Is my betta's water OK?”
“My kid's fish can't die this week.”
“Last time my fish died and I never knew why.”
Beginner guides
All 10 guides →
Short answers first
Questions
How long does it take to cycle a new fish tank?
Usually 4 to 8 weeks. It is done when 2 ppm of ammonia turns into 0 ammonia and 0 nitrite within 24 hours, two days in a row.
How many fish can I put in a 10 gallon tank?
It depends on the species: one betta, or a school of 6 to 8 nano fish. The stocking calculator checks your exact mix.
My fish are already in an uncycled tank. What do I do?
Test every day. At 0.25 ppm ammonia or nitrite, change 30–50% of the water and feed less. At 1 ppm, change water right away.
The TankCoach app
Your coach for the first 30 days
iPhone and Android, in development.
Get early access⟳Cycle Coach
📈Test log & charts
🐟60 species
⏰Reminders
9:41100%
Living room tank
20 gal · fish-in · day 12
Nitrite spike
≈ 2 weeks to go
Today
💧Change 40% of the water
Feed once, lightly