Free tools
Aquarium Tools & Quick-Reference Guides
Simple reference tables and trusted gear that take the guesswork out of fishkeeping. Bookmark this page — it’s the quick answer to “is my tank okay?”
Know your numbers
Safe Water Parameters
| Test | Safe target | Why it matters |
|---|---|---|
| Ammonia (NH₃) | 0 ppm | The #1 killer in new tanks. Any reading is harmful. |
| Nitrite (NO₂) | 0 ppm | Stops fish carrying oxygen in their blood. |
| Nitrate (NO₃) | < 20–40 ppm | Stresses fish and feeds algae when high. |
| pH | stable | Stability matters more than a “perfect” number. |
| Temperature | 24–27°C / 75–80°F | Verify with a thermometer — heaters drift. |
Quick guide
Water-Change Quick Guide
| Situation | How much | How often |
|---|---|---|
| Healthy routine | 20–30% | Weekly |
| New / cycling tank | 20–30% | Every 1–3 days |
| Ammonia or nitrite present | 25–50% | Daily until 0 |
| Heavily stocked | 30–40% | Twice weekly |
Always dechlorinate and temperature-match new water. Never do a 100% change — it crashes your beneficial bacteria.
The essentials
Tools Every Beginner Should Own
Liquid Test Kit
The single most important tool. Catches problems before fish suffer.
See our pickDechlorinator
Neutralises chlorine in tap water instantly.
See our pickAir Pump + Stone
Cheap insurance against low-oxygen emergencies.
See our pickThermometer
Catches a stuck heater before it cooks or chills the tank.
See our pick
Get the Free Aquarium Survival Checklist
Keep these numbers in your pocket. The 1-page checklist that helps you catch tank problems early.
Good questions
Tools FAQ
What’s the most important aquarium tool?
A liquid water test kit. The things that kill fish — ammonia and nitrite — are invisible, and a test kit is the only way to catch them early. It pays for itself the first time it prevents a loss.
How often should I test my water?
Weekly for an established tank, and every 1–2 days for a new tank that’s still cycling or any time fish look unwell. Test before you change anything so you act on the real numbers.
Are test strips good enough?
Strips are convenient for a quick check, but liquid kits are far more accurate — especially for ammonia. If you can only own one tool, make it a liquid kit.