Keeping Your Aquarium Healthy
Getting an aquarium established is only the beginning. Once your fish are settled in, regular maintenance keeps the water healthy, the equipment working properly and the aquarium looking its best.
The good news is that aquarium maintenance doesn't need to be complicated.
A well-established aquarium generally benefits more from small, regular maintenance than occasional massive clean-outs.
One of the biggest mistakes new fishkeepers make is actually cleaning too much. Your aquarium contains beneficial bacteria that form an important part of its biological filtration, so the aim isn't to sterilise everything.
Freshwater and marine aquariums also have different maintenance requirements, so we've separated this guide into two clear sections:
PART ONE — TROPICAL FRESHWATER AQUARIUM MAINTENANCE
PART TWO — MARINE AQUARIUM MAINTENANCE
First, one rule applies to both:
Regular maintenance and observation are far better than waiting until something goes wrong.
PART ONE
TROPICAL FRESHWATER AQUARIUM MAINTENANCE
Once established, most freshwater aquariums are relatively straightforward to maintain.
A regular routine usually consists of water changes, water testing, cleaning the glass, maintaining the filter and keeping an eye on your fish and equipment.
1. Check Your Aquarium Every Day
Not every maintenance job involves getting your hands wet.
One of the most useful things you can do is simply look at your aquarium every day.
While feeding, check:
- Are all the fish present?
- Are they behaving normally?
- Are they feeding normally?
- Is anyone breathing heavily?
- Are there signs of damage or disease?
- Is the filter running?
- Is the heater working?
- Is the temperature correct?
- Are there any leaks?
- Does anything simply look different?
When you see the aquarium every day, you quickly learn what's normal.
That makes unusual behaviour much easier to spot early.
2. Regular Water Changes
Water changes are one of the most important parts of freshwater aquarium maintenance.
Over time, nitrate and other dissolved waste products can accumulate in the aquarium.
A partial water change removes some of these while replacing minerals and refreshing the water.
There isn't one percentage or schedule that's perfect for every aquarium. Stocking level, feeding, filtration, plants and nitrate levels all influence how frequently water changes are required.
For many typical freshwater aquariums, regular partial water changes are a good starting point, with your water test results helping determine whether the routine needs adjusting.
Avoid routinely replacing all of the aquarium water.
A normal maintenance water change should generally be a partial change, not a complete strip-down of the aquarium.
3. Always Treat Tap Water
If you're filling a freshwater aquarium with tap water, use an appropriate water conditioner where required.
Tap water disinfectants such as chlorine or chloramine are designed to kill microorganisms — exactly what we don't want affecting the beneficial bacteria in an aquarium.
Use an appropriate conditioner according to the manufacturer's instructions.
Try to ensure replacement water is also reasonably close to the aquarium's temperature before adding it.
4. Test Your Water
Don't wait until the fish look unwell before testing the aquarium.
Regular testing helps you identify changes before they become serious problems.
For a freshwater aquarium, some of the most useful parameters include:
Ammonia — should not be allowed to accumulate.
Nitrite — should not be allowed to accumulate.
Nitrate — naturally accumulates and can help indicate when maintenance is required.
pH — useful for understanding the conditions your livestock are living in.
Depending on the livestock you keep, GH and KH may also be useful.
Your test kit is one of the best early-warning systems your aquarium has.
5. Clean the Substrate
Waste, uneaten food and other debris can collect on or within the substrate.
During a water change, a gravel cleaner or siphon can be used to remove this material.
How thoroughly you clean depends partly on the aquarium.
A heavily planted aquarium may be treated differently from a tank with open gravel.
Sand also requires a different technique from coarse gravel because debris tends to remain on the surface rather than sinking deeply between the grains.
The aim is to remove excess waste — not make the aquarium clinically sterile.
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6. Clean the Glass
A little algae on aquarium glass is perfectly normal.
An algae pad, scraper or suitable magnetic cleaner can make it easy to remove.
How often you need to do this depends on lighting, nutrients and the individual aquarium.
If algae suddenly becomes excessive, don't just keep scraping it away.
Consider why it's increasing.
Lighting duration, excess nutrients, overfeeding and maintenance can all contribute.
We'll cover this in much more detail in our dedicated aquarium algae guide.
SHOP AQUARIUM CLEANING EQUIPMENT →
7. Maintain Your Filter — But Don't Sterilise It
Your filter doesn't just collect dirt.
It's also home to a large population of beneficial bacteria that help process fish waste.
That means filter maintenance needs to be done carefully.
Mechanical media such as sponges can eventually become clogged and need cleaning.
When appropriate, these can often be gently rinsed using water removed from the aquarium during a water change, rather than aggressively washing everything under untreated tap water.
Don't replace every piece of filter media simply because it looks dirty.
And don't routinely replace all biological media at the same time.
Doing so can remove a significant proportion of the bacteria supporting your aquarium.
8. Not All Filter Media Needs Replacing at the Same Time
Different filter media performs different jobs.
Mechanical media
Catches physical debris.
Biological media
Provides surface area for beneficial bacteria.
Chemical media
Can be used for specific purposes and may require replacement according to the particular product.
Follow the manufacturer's instructions, but remember:
Biological media doesn't automatically need throwing away because it's dirty.
Often it simply requires careful maintenance.
9. Check the Filter Flow
You gradually become accustomed to how much water your filter normally moves.
If the flow suddenly becomes weaker, investigate.
The intake may be blocked.
A sponge or pre-filter may need cleaning.
The impeller may require maintenance.
Hoses on an external filter may have accumulated debris.
Reduced flow is often an early indication that some filter maintenance is due.
10. Look After Live Plants
If you keep live aquarium plants, they'll become part of your maintenance routine.
You may need to:
- Remove dead leaves
- Trim excessive growth
- Replant cuttings
- Remove floating debris
- Add fertiliser where appropriate
- Maintain suitable lighting
Healthy plants can transform an aquarium, but they still need care.
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11. Don't Overfeed
Maintenance starts before anything reaches the gravel cleaner.
Excess food means excess waste.
Feed an appropriate amount for the livestock you keep and watch the fish while they're eating.
Food constantly falling to the bottom and remaining uneaten may indicate that you're feeding too much or using an unsuitable food.
Overfeeding can contribute to poor water quality and algae problems.
12. Check Your Equipment
Every so often, inspect the equipment rather than simply assuming it's working.
Check:
- Heater
- Thermometer
- Filter
- Air pump
- Lighting
- Timers
- Cables
- Pipework and hoses
- Aquarium seals and surrounding area
Equipment doesn't always stop working dramatically.
Sometimes performance gradually declines.
Regular observation helps you catch problems sooner.
13. Don't Clean Everything at Once
This is worth emphasising.
You don't need to:
Change most of the water + replace all the filter media + scrub every decoration + deep-clean the substrate + completely dismantle the filter
all on the same day.
A mature aquarium is a living biological system.
Maintain it — don't sterilise it.
A sensible routine of smaller maintenance jobs is usually much better than repeatedly stripping everything back.
A SIMPLE FRESHWATER ROUTINE
DAILY
Feed appropriately and check livestock, temperature and equipment.
REGULARLY
Test the water, perform partial water changes as required, remove debris and clean the viewing glass.
AS REQUIRED
Clean filter sponges/media carefully, maintain plants, clean equipment and inspect pumps/impellers.
Every aquarium is different, so use the condition of the aquarium and your water test results to adjust the routine.
EXPLORE FRESHWATER AQUARIUM PRODUCTS →
PART TWO
MARINE AQUARIUM MAINTENANCE
Marine aquariums follow many of the same basic principles, but there are additional parameters and equipment to consider.
Stability becomes particularly important — especially once you begin keeping corals and more sensitive livestock.
The aim isn't to constantly chase numbers.
The aim is to create appropriate conditions and keep them reasonably stable.
1. Check the Aquarium Every Day
Just like freshwater, observation is one of your best maintenance tools.
Check:
- Fish behaviour
- Feeding response
- Coral appearance
- Invertebrate behaviour
- Water temperature
- Filter and pump operation
- Water circulation
- Protein skimmer operation
- Water level
- Automatic top-off equipment
- Any unusual noises
- Leaks
You know your aquarium better than anyone else.
If something suddenly looks different, investigate.
2. Salinity Is Fundamental
One of the obvious differences between freshwater and marine aquariums is salinity.
Marine livestock requires seawater maintained at an appropriate and stable salinity.
Use a suitable instrument such as a refractometer or reliable salinity meter to monitor it.
And remember:
Evaporation removes freshwater — not salt.
As water evaporates, the salt remains behind, meaning salinity can increase.
That's why evaporation is normally replaced with fresh RO/RODI water, not additional saltwater.
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3. Top Off Evaporation
Marine aquariums can lose a surprising amount of water through evaporation.
Replacing this manually works, but an automatic top-off system (ATO) can make maintaining a stable water level much easier.
An ATO detects the falling water level and replaces the evaporated freshwater.
This helps reduce swings in salinity.
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4. Marine Water Changes
Marine aquariums also benefit from appropriate regular water changes.
The difference is that replacement seawater needs to be prepared correctly.
If mixing your own saltwater:
- Use suitable source water
- Use a quality marine salt
- Mix according to instructions
- Check salinity
- Bring the water to an appropriate temperature
- Ensure it is properly mixed before use
Never simply add dry marine salt directly to a stocked aquarium to correct routine water-change volume.
5. Use Suitable Source Water
Water quality matters enormously in marine systems.
RO or RODI water is commonly used because it gives the aquarist much greater control over what's going into the aquarium.
Tap water can contain nitrate, phosphate, silicates, metals and other substances that may be undesirable in a marine or reef system.
Using purified source water gives you a much cleaner starting point.
6. Test Your Marine Aquarium
For a basic fish-only marine aquarium, you'll still want to understand:
- Ammonia
- Nitrite
- Nitrate
- pH
- Salinity
- Temperature
Once you move into reef keeping, additional parameters become increasingly important.
These can include:
- Alkalinity (KH)
- Calcium
- Magnesium
- Phosphate
The exact testing routine depends on what you're keeping.
A lightly stocked fish-only aquarium doesn't necessarily require the same testing regime as an established SPS reef.
7. Reef Aquariums Need Greater Stability
Once corals enter the picture, maintaining stable water chemistry becomes increasingly important.
Corals use elements from the water as they grow.
In more demanding reef systems, water changes alone may eventually be insufficient to maintain everything at the desired level.
Depending on the aquarium, this can lead to supplementation of parameters such as:
- Alkalinity
- Calcium
- Magnesium
Products such as balanced reef supplements can make this easier, but supplementation should be based on testing and actual consumption.
Don't dose something simply because you own a reef aquarium.
Test first.
8. Maintain Your Protein Skimmer
If your marine aquarium uses a protein skimmer, it requires regular maintenance.
Empty and clean the collection cup as necessary.
Check the air intake.
Inspect the pump.
Watch for changes in performance.
A dirty skimmer neck can reduce efficiency, while blocked airways or pumps can affect operation.
You'll soon learn what normal skimmer performance looks like for your particular system.
9. Maintain Pumps & Flow Equipment
Water movement is extremely important in marine aquariums.
Powerheads and circulation pumps can gradually become coated with algae, calcium deposits and debris.
This can reduce performance.
Periodically inspect and clean them according to the manufacturer's instructions.
Don't wait until a pump stops completely before looking at it.
10. Clean Mechanical Filtration
Filter socks, filter floss, sponges and other mechanical media physically trap waste.
That's useful — provided the trapped waste is eventually removed.
Allowing heavily soiled mechanical filtration to remain indefinitely means that material is still breaking down within the system.
Clean or replace appropriate mechanical filtration as required.
11. Clean the Glass
Marine aquariums also develop algae on the viewing panels.
Use suitable algae cleaning equipment and take particular care with acrylic aquariums, where inappropriate tools can cause scratches.
If algae becomes excessive, look beyond simply cleaning the glass.
Consider nutrients, lighting, feeding, source water and maintenance.
SHOP AQUARIUM CLEANING EQUIPMENT →
12. Keep an Eye on Nitrate & Phosphate
Nitrate and phosphate are important nutrients within a marine aquarium.
The aim isn't necessarily to blindly drive everything to zero.
Instead, understand the requirements of the system you're keeping and watch for significant changes.
Unexpected increases can indicate issues such as:
- Overfeeding
- Accumulated waste
- Poor mechanical filtration maintenance
- Livestock losses
- Inadequate export
- Source-water problems
Testing allows you to see what's happening rather than guessing.
13. Inspect Corals, Fish & Invertebrates
A reef aquarium gives you even more animals to observe.
Look for changes in:
- Coral extension
- Colour
- Tissue condition
- Feeding
- Fish behaviour
- Breathing
- Invertebrate activity
A coral remaining closed doesn't automatically tell you exactly what's wrong.
But a sudden change is a reason to investigate the aquarium's conditions.
14. Don't Chase Numbers
This is particularly important with marine aquariums.
You can easily find recommendations online for the “perfect” value of almost every parameter.
The danger is constantly adding products and making adjustments trying to hit an exact number.
Appropriate and stable is often more valuable than constantly changing the aquarium in pursuit of perfection.
If something needs correcting, make sensible adjustments rather than causing another sudden swing.
A SIMPLE MARINE ROUTINE
DAILY
Check livestock, temperature, equipment, circulation and water level. Top off evaporation with appropriate freshwater or ensure your ATO is operating correctly.
REGULARLY
Check salinity and important water parameters, clean the glass, perform appropriate water changes and maintain mechanical filtration.
AS REQUIRED
Clean pumps, service the protein skimmer, maintain filters, inspect equipment and test additional reef parameters.
REEF AQUARIUMS
Monitor alkalinity, calcium, magnesium, phosphate and other relevant parameters according to the livestock and demands of the system.
THINGS BOTH FRESHWATER & MARINE KEEPERS SHOULD AVOID
Whether you're keeping freshwater or marine livestock, there are several common mistakes worth avoiding:
- Don't overfeed.
- Don't completely strip down a healthy aquarium unnecessarily.
- Don't replace all biological filter media at once.
- Don't add chemicals without understanding why you're using them.
- Don't ignore changes in fish behaviour.
- Don't rely on appearance alone to judge water quality.
- Don't wait until there's a problem before testing the water.
- Don't assume equipment is working simply because it's switched on.
And perhaps most importantly:
Don't panic and start changing everything at once when something goes wrong.
Test the water, inspect the equipment and work through the possible causes logically.
Maintenance Gets Easier
When you're new to fishkeeping, aquarium maintenance can sound like a long list of jobs.
In reality, once you establish a routine, most of it becomes second nature.
You'll know how your fish normally behave.
You'll recognise when the filter flow has dropped.
You'll know roughly how quickly algae appears.
You'll understand how often your aquarium normally requires a water change.
And your test results will begin showing you how the aquarium behaves over time.
Consistency is the key.
A little regular maintenance can prevent much larger problems later.
Need Help With Aquarium Maintenance?
Whether you're maintaining your first tropical aquarium or running a fully stocked marine reef, Tropical Supplies can help with the equipment, treatments, test kits, filter media, foods and other products needed to keep your aquarium running properly.
And if something doesn't look right, bring us as much information as possible — including your aquarium size, livestock, water test results and details of the equipment you're using.
Visit us in store and speak to a member of the Tropical Supplies team.