Free tools
Aquarium Tools & Water Parameter Guide
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
Tested & trusted
Where to Get Them
Top pick Liquid Water Test Kit
The first thing to buy. Reveals the ammonia, nitrite, and nitrate behind most fish problems — far more accurate than strips.
Check price Affiliate linkEssential Water Dechlorinator
Removes chlorine and detoxifies ammonia and nitrite — the one bottle to keep on hand for water changes and emergencies.
Check price Affiliate linkEmergency kit Air Pump and Air Stone
Boosts dissolved oxygen and surface agitation fast — the go-to fix when fish are gasping or the tank runs warm.
Check price Affiliate linkAdjustable Heater
A reliable adjustable heater holds a stable temperature. Pair it with a separate thermometer and never trust the dial alone.
Check price Affiliate linkGravel Vacuum Siphon
Makes water changes quick and pulls trapped waste out of the substrate — the hidden fuel behind ammonia and algae.
Check price Affiliate linkDigital Aquarium Thermometer
Verifies the real temperature so a stuck or failing heater never catches you out.
Check price Affiliate link
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.
Which aquarium tool to use first
Tools are most useful when they answer a specific decision. Do not test or calculate just to collect numbers. Use each tool to decide what to do next.
- Use the symptoms checker when fish behavior changes and you need to narrow the cause quickly.
- Use the water change calculator before emergency water changes so you do not shock the tank with too much change at once.
- Use stocking and volume guidance before buying fish, not after the tank is crowded.
- Use checklist pages before setup days, maintenance days, and new livestock purchases.
The practical order is simple: diagnose the problem, confirm the water, make the smallest safe correction, then track whether the tank improves.
Using tools without overcorrecting
Aquarium tools should prevent panic, not create it. A calculator or checker gives you a safer starting point, but the tank still needs observation. If a tool suggests a water change, match temperature and dechlorinate. If the symptoms checker points toward oxygen, increase surface movement and then confirm water quality.
Use tools before purchases whenever possible. Tank volume affects heater size, stocking, medication dosing, and water-change math. Stocking choices affect maintenance. A checklist catches missing setup steps before livestock is involved. The earlier you use the tool, the less expensive the mistake becomes.
Keep a simple record of the numbers you calculate or test. A single reading can be misleading, but a trend is useful. If nitrate rises each week, if temperature swings at night, or if TDS creeps upward after top-offs, the pattern tells you what routine needs to change.