Water Testing — Measuring and Understanding Parameters

Master water testing! Ammonia, nitrite, nitrate, pH, GH, KH — what to test, how to test, and what results mean.

wasserwerte · 9 Min. Lesezeit · water parameters, testing, ammonia, nitrite, nitrate, pH

Water Testing — Measuring and Understanding Parameters

Water testing is your window into invisible aquarium health. Here's how to test accurately and understand what the numbers mean.

Why Test Water?

You can't see most problems:

Water tests reveal:

Test regularly = catch problems early = save fish lives.

Essential Test Parameters

1. Ammonia (NH₃/NH₄⁺)

What it is: Fish waste, uneaten food decomposition product

Toxicity: EXTREMELY TOXIC even at 0.25 ppm

Safe level: 0 ppm (always!)

Dangerous levels:

Causes of ammonia spikes:

How to fix:

2. Nitrite (NO₂⁻)

What it is: Intermediate product (ammonia → nitrite → nitrate)

Toxicity: VERY TOXIC at 0.5+ ppm

Safe level: 0 ppm (always!)

Dangerous levels:

Causes of nitrite spikes:

How to fix:

During cycling: Nitrite can spike to 5-10+ ppm — this is normal! Wait it out.

3. Nitrate (NO₃⁻)

What it is: Final product of nitrogen cycle

Toxicity: Low toxicity (compared to ammonia/nitrite)

Safe levels:

How it accumulates:

How to lower:

Reef tanks: Keep <5-10 ppm (corals are sensitive)

4. pH (Acidity/Alkalinity)

Scale: 0-14 (7 = neutral)

Ideal pH by fish type:

Stability matters more than perfection!

Stable pH 7.5 > fluctuating 6.8-7.5

Causes of pH swings:

How to stabilize pH:

5. KH (Carbonate Hardness / Alkalinity)

What it is: Buffering capacity (resists pH changes)

Measured in: °dH or ppm

Ideal levels:

Why it matters:

How to raise KH:

How to lower KH:

6. GH (General Hardness)

What it is: Dissolved minerals (calcium, magnesium)

Measured in: °dH or ppm

Ideal by fish type:

Why it matters:

How to raise GH:

How to lower GH:

Testing Methods

1. Liquid Test Kits (BEST!)

Recommended: API Master Test Kit

Includes:

Pros:

Cons:

How to use:

Tip: Read results on white background for accuracy.

2. Test Strips (NOT RECOMMENDED)

Pros:

Cons:

Only use for rough estimates (e.g., checking pH trend).

3. Digital Meters

Examples:

Pros:

Cons:

Best for: Serious hobbyists, reef tanks

Testing Schedule

New Tank (Cycling):

Test daily:

Goal: Track cycling progress

Established Tank (3+ months):

Test weekly:

Test monthly:

Problem Tank (Disease, Deaths, Algae):

Test daily until resolved:

After Major Changes:

Test daily for 1 week after:

Interpreting Test Results

Scenario 1: Ammonia 0.5 ppm, Nitrite 0, Nitrate 10 ppm

Problem: Ammonia spike (but tank is cycled — nitrate present)

Likely cause: Overfeeding, dead fish, filter issue

Action:

Scenario 2: Ammonia 0, Nitrite 3 ppm, Nitrate 5 ppm

Problem: Nitrite spike (tank cycling or cycle crash)

Action:

Scenario 3: Ammonia 0, Nitrite 0, Nitrate 80 ppm

Problem: Nitrate buildup (infrequent water changes)

Action:

Scenario 4: pH 6.0 (was 7.2 last week)

Problem: pH crash (KH depleted)

Action:

Common Testing Mistakes

1. Not Shaking Reagent Bottles

Nitrate test bottle #2 MUST be shaken vigorously for 30 seconds!

Failure to shake = false low readings.

2. Testing Too Soon After Water Change

Wait 1-2 hours after water change before testing (let parameters stabilize).

3. Using Expired Test Kits

Check expiration dates! Old kits give false readings.

Store in cool, dry place (not bathroom).

4. Reading in Poor Lighting

Use natural daylight or bright white light.

Yellow/dim lighting skews color readings.

5. Not Testing Tap Water

Test your source water (tap/RO) to establish baseline!

Example:

Conclusion

Water testing is your early warning system.

Essential tests:

Testing schedule:

Invest in API Master Test Kit (€25-35) — best value for accurate results.

Test, log, learn patterns — you'll predict problems before they happen!

"Test, don't guess!"

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