All About Water Parameters: A Beginner’s Guide for Fishkeepers & Aquascapers

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All About Water Parameters: The Beginner’s Guide to Healthy Aquariums

Keeping fish and plants happy doesn’t just come down to feeding them and switching on the filter — the real secret is in the water parameters. These invisible measurements determine whether your aquarium is safe, stable, and thriving.

At Horizon Aquatics, we often meet newcomers who proudly say their pH is fine, but then struggle with fish health. The truth is: pH is only one piece of the puzzle. The most important things to understand are ammonia, nitrite, nitrate, and the nitrogen cycle.

This guide explains water parameters in simple terms, why they matter, how they connect to each other, and how to keep them under control.

Why Are Water Parameters Important?

In the wild, rivers and lakes are naturally balanced. But an aquarium is a closed system where waste builds up quickly. Without proper control, water can turn toxic before you even realise there’s a problem.

Monitoring water parameters helps you:

Protect fish from invisible toxins
Support healthy plant growth
Prevent algae outbreaks
Diagnose problems when things go wrong

Think of water parameters as the vital signs of your aquarium.

Key Aquarium Water Parameters Explained

Ammonia / Ammonium (NH₃/NH₄⁺)

Comes from fish waste, uneaten food, and rotting plants and Aquasoil when it is first introduced to a tank
Highly toxic — even tiny amounts can kill fish.
Safe level: 0 ppm.

Nitrite (NO₂⁻)

Produced when bacteria break down ammonia.
Still toxic — it prevents fish blood from carrying oxygen.
Safe level: 0 ppm.

Nitrate (NO₃⁻)

Final stage of the nitrogen cycle.
Less harmful, but high levels stress fish and fuel algae.
Safe level: Below 40 ppm (ideally under 20 ppm in aquascapes).
Control: Regular water changes and healthy plant growth.

pH (Acidity/Alkalinity)

Measures how acidic or alkaline the water is.
Most fish do well between 6.5–7.5.
Stability is more important than the exact number.
With CO₂ injection: pH naturally swings during the day. This is safe because it’s controlled — far better than random swings caused by unstable water chemistry.

GH (General Hardness)

Measures dissolved minerals like calcium and magnesium.
Important for fish health and plant growth.
Livebearers (e.g. guppies) prefer harder water; tetras prefer softer.

KH (Carbonate Hardness)

Buffers pH and keeps it stable.
Low KH can make pH unstable, but in aquascaping, weekly water changes make low KH far less of a problem.
Safe range: 3–8 dKH for most aquariums (Caridina shrimp require 0 KH)

Temperature

Different fish have different requirements.
Most tropical tanks thrive at 24–26°C (75–79°F).

Newly planted dutch aquarium going through the cycling phase

The Nitrogen Cycle: The Heart of Fishkeeping

The nitrogen cycle is the single most important process in your aquarium. It makes the difference between a safe, balanced tank and one where fish quickly get sick.

Ammonia is produced – from fish waste, food, and organics.
Bacteria convert ammonia into nitrite (Nitrosomonas bacteria).
Other bacteria convert nitrite into nitrate (Nitrobacter bacteria).
Nitrate is removed by water changes and plant uptake.

Why It Matters

In a new tank, bacteria aren’t established, so ammonia and nitrite build up quickly.
A tank is cycled when beneficial bacteria colonies are strong enough to keep ammonia and nitrite at 0 ppm, while nitrates rise slowly over time.
The cycle can take 4–6 weeks in a new setup.

How to Tell if Your Tank is Cycled

Ammonia = 0 ppm
Nitrite = 0 ppm
Nitrate = rising gradually

👉 Using a good test kit (we recommend NT Labs) is the only reliable way to monitor this process.

Tips for Faster Cycling

Seed your filter with media from a mature tank.
Add bottled bacteria starters such as Seachem Stability and NT Labs Satus (this does not mean you can add fish from day one)
Be patient — rushing cycling often results in fish losses.

The Role of Water Changes

Even with the best filter in the world, water changes are non-negotiable. They:

Dilute excess nitrates and waste
Replenish minerals for fish and plants
Prevent pH swings
Keep aquariums looking crystal clear

👉 Aim for a 25–50% water change every week. It’s the single best habit any aquarist can build.

How to Test Your Water

The only way to know what’s really happening in your tank is to test it. At Horizon Aquatics, we recommend NT Labs Test Kits because they’re accurate, easy to use, and cover all the essential parameters.

Test ammonia, nitrite, nitrate, and pH weekly.
Check KH and GH if keeping sensitive species or a high-tech aquascape.
Record results so you can spot trends before problems appear.

FAQs About Aquarium Water Parameters

Q: Do I need to worry about pH if my ammonia and nitrite are fine?
A: Not really — stability matters more than the exact number. Fish adapt better to a steady pH than to sudden changes.

Q: Why does my pH drop when I inject CO₂?
A: CO₂ naturally lowers pH during the day. This is safe and controlled, unlike random swings caused by low KH.

Q: How often should I change water?
A: Every week. 25–50% is ideal for keeping nitrates down and parameters stable.

Q: My KH is low — is that bad?
A: Not necessarily. In planted tanks with regular weekly water changes, low KH is usually not a problem.

Final Thoughts

Water parameters may sound complicated at first, but once you understand the basics, everything falls into place. Focus first on ammonia, nitrite, and nitrate, then look at pH, GH, and KH for fine-tuning. Above all, remember: