31/10/2026
🐠💧 AQUARIUM KNOW-HOW – EPISODE 4! 💧🐠
UNDERSTANDING AQUARIUM WATER PARAMETERS – WHAT ARE WE TESTING FOR, AND WHY?
Welcome back to another instalment of Aquarium Know-How, brought to you by your locally owned and operated Hobart Pet Centre! 🐟🪸
Over our first three episodes, we've explored setting up freshwater and marine aquariums and, most recently, the fascinating nitrogen cycle.
Now that we understand how beneficial bacteria help keep our aquariums healthy, it's time to look at something equally important...
🔬 WATER CHEMISTRY!
Don't worry, you don't need a science degree to understand it! 😁
The water in your aquarium might look crystal clear, but appearances can be deceiving. Understanding a few basic water parameters can make an enormous difference to the health and wellbeing of your aquatic inhabitants.
Let's explore six important parameters every freshwater aquarium keeper should understand.
💧 1. pH – HOW ACIDIC OR ALKALINE IS YOUR WATER?
pH measures how acidic or alkaline your aquarium water is on a scale from 0 to 14.
• Below 7 = Acidic
• 7 = Neutral
• Above 7 = Alkaline
Different fish prefer different pH ranges. Many tropical community fish thrive around pH 6.5–7.5, while some African cichlids prefer considerably more alkaline conditions.
⭐ TOP TIP: Stability is often more important than achieving a particular pH number, provided that number is appropriate for the species you're keeping. Sudden changes can cause significant stress!
☠️ 2. AMMONIA (NH₃/NH₄⁺) – THE INVISIBLE DANGER!
Ammonia is produced through fish waste, decomposing food and other organic material.
It's highly toxic to fish, particularly in its un-ionised form (NH₃).
Fortunately, beneficial bacteria in an established aquarium convert ammonia into nitrite as part of the nitrogen cycle we explored last week.
✅ Our target: Zero detectable total ammonia on a standard aquarium test kit.
Remember, ammonia becomes particularly dangerous when biological filtration hasn't fully established or something disrupts the nitrogen cycle.
⚠️ 3. NITRITE (NO₂⁻) – ANOTHER ONE TO WATCH!
Nitrite is produced when beneficial bacteria begin processing ammonia.
Unfortunately, nitrite is also toxic to fish because it interferes with their ability to transport oxygen through their bloodstream.
A second group of beneficial bacteria converts nitrite into nitrate.
✅ Our target: Zero detectable nitrite.
If you're detecting ammonia or nitrite in an established freshwater aquarium, it's time to investigate!
🌿 4. NITRATE (NO₃⁻) – THE END PRODUCT OF THE NITROGEN CYCLE
Nitrate is considerably less toxic than ammonia or nitrite, but that doesn't mean we should ignore it.
Over time, nitrate can accumulate through feeding and biological waste.
Elevated concentrations can contribute to poor fish health and unwanted algae growth.
For many freshwater community aquariums, keeping nitrate below approximately 20–40 ppm is a reasonable general guide, although some sensitive species require lower concentrations.
Regular partial water changes, appropriate feeding and healthy aquatic plants can all help manage nitrate levels.
🪨 5. GH – GENERAL HARDNESS
GH measures the concentration of dissolved calcium and magnesium ions in your aquarium water.
Some fish naturally inhabit soft water, while others thrive in harder water.
For example:
🐟 Discus and many South American species generally prefer softer water.
🐠 African Rift Lake cichlids typically prefer harder, mineral-rich water.
Understanding GH helps us select fish suited to our water conditions rather than constantly trying to change those conditions.
🧪 6. KH – CARBONATE HARDNESS
KH measures the water's acid-neutralising capacity, primarily provided by bicarbonates and carbonates.
Think of KH as your aquarium's pH shock absorber!
Adequate KH helps resist sudden drops in pH caused by acids naturally produced within the aquarium.
Very low KH can leave an aquarium vulnerable to significant pH fluctuations.
However, different aquarium environments have different requirements, so there isn't one perfect KH value for every system.
🌡️ AND DON'T FORGET TEMPERATURE!
Although it's not a chemical parameter, temperature is just as important!
Different fish have different temperature requirements, and maintaining a suitable, stable temperature is essential for their health.
Many tropical community aquariums operate around 24–26°C, but always research the requirements of your particular species.
🪸 WHAT ABOUT MARINE AQUARIUMS?
All these principles are relevant to marine aquariums too, but saltwater systems have some additional considerations.
Marine aquarium keepers also need to pay particular attention to:
🌊 Salinity – The concentration of dissolved salts.
🪸 Alkalinity – Essential for pH stability and coral calcification.
🦀 Calcium – Important for coral skeletons and other calcifying organisms.
🔬 Magnesium – Helps maintain the chemical balance between calcium and alkalinity.
🌿 Phosphate – An essential nutrient that needs careful management, particularly in reef systems.
We'll explore marine water chemistry in greater detail in a future episode!
💙 SO, HOW OFTEN SHOULD YOU TEST YOUR WATER?
For a newly established aquarium, testing ammonia and nitrite every day or two is a sensible approach while the biological filter develops.
Once your aquarium is established and stable, weekly testing is a good starting point, with adjustments depending on your aquarium and its inhabitants.
And remember, if your fish are behaving unusually, testing your water should be one of your first steps!
🐠 OUR AQUARIUM KNOW-HOW QUESTION OF THE WEEK! 🤔
Your aquarium water looks absolutely crystal clear. Does that necessarily mean it's healthy and safe for your fish?
A) Yes! Clear water means everything is working perfectly.
B) Not necessarily! Dangerous substances can be present even when the water looks perfectly clear.
C) Only if the fish are swimming around happily.
Let us know your answer in the comments! 👇😁
🏪 NEED A LITTLE HELP UNDERSTANDING YOUR AQUARIUM WATER?
At Hobart Pet Centre, we're always happy to help you better understand your aquarium, discuss suitable testing equipment and offer practical advice on maintaining a healthy aquatic environment.
Whether you're just starting out or have been keeping fish for years, there's always something new to learn!
📍 Hobart Pet Centre – 148 Liverpool Street, Hobart.
🐟 COMING UP IN EPISODE 5!
CHOOSING COMPATIBLE FISH – BECAUSE NOT EVERY FISH MAKES A GOOD NEIGHBOUR! 🐠
Until next time, happy fishkeeping! 💙
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