Menu
  • Unit A225 4 - 6 Greatorex Street, London, England, E1 5NF
  • Enterprise Award Winner 2026
  • 0330 043 3832
  • info@aquassi.co.uk
Facebook X-twitter Youtube Tiktok Pinterest Paypal

Troubleshooting

Aquarium Troubleshooting: Common Problems, Causes & Solutions

Even a well-maintained aquarium can occasionally develop problems. Cloudy water, algae, unusual fish behaviour, unpleasant smells and equipment issues are all common challenges for aquarium keepers.

The key to successful aquarium troubleshooting is finding the underlying cause rather than simply treating the symptom.

At Aquassi Ltd, we believe a healthy aquarium comes from understanding the relationship between fish, plants, filtration, lighting, water quality, CO₂ and maintenance.

Aquarium Troubleshooting Basics

When something changes, avoid making several major changes at once.

Start by asking:

  1. What has changed?
  2. When did the problem begin?
  3. Are all fish affected?
  4. Have new fish or plants been added?
  5. Has aquarium equipment changed?
  6. Have water parameters changed?
  7. Has the feeding routine changed?

This information can help identify the cause.

Fish Gasping at the Surface

Fish repeatedly gasping at the surface can indicate a serious problem.

Possible causes include:

Check the filter, temperature and water parameters immediately.

Increasing appropriate surface agitation can help improve gas exchange while you investigate the cause.

Fish Hiding

Hiding is normal for many species, but sudden excessive hiding can indicate:

Check the aquarium environment and observe interactions between tank mates.

Fish Not Eating

A temporary reduction in appetite can occur after introducing fish or making changes to the aquarium.

Persistent loss of appetite can indicate:

Check water parameters before assuming the problem is disease.

Fish Swimming Erratically

Erratic swimming may be associated with:

Observe the fish carefully and test the aquarium water.

Fish Sitting on the Bottom

Some species naturally spend considerable time on the substrate.

However, if an ordinarily active fish suddenly becomes inactive, investigate:

Look for additional symptoms.

Fish Clamped Fins

Clamped fins can be a sign of stress or illness.

Potential causes include:

Check water parameters first.

Aquarium Water Is Cloudy

Cloudy water is a common aquarium problem.

Possible causes include:

The appearance of the cloudiness can provide clues about the cause.

Avoid repeatedly performing large interventions without understanding what is happening.

White or Milky Cloudy Water

A white or milky appearance is often associated with suspended microorganisms, particularly in newly established aquariums.

A bacterial bloom may occur while the biological ecosystem is developing.

Maintain appropriate filtration and monitor ammonia and nitrite.

Green Water

Green water occurs when microscopic algae multiply throughout the water column.

Potential contributing factors include:

Severe green-water problems may require additional filtration or UV clarification.

Brown Algae

Brown algae is often actually diatoms.

It commonly appears in newer aquariums as a dusty brown coating.

It may naturally decline as the aquarium matures.

Manual removal, appropriate maintenance and healthy plant growth can help.

Green Algae

Green algae can appear as:

Review:

Hair Algae

Hair algae can quickly become tangled around plants and hardscape.

Remove excessive growth manually and review the aquarium’s balance.

Avoid simply adding large numbers of algae-eating animals.

Green Spot Algae

Small green spots on aquarium glass and plant leaves are often associated with green spot algae.

Clean the glass regularly and review plant growth and nutrient management.

Aquarium Smells Bad

A strong smell may indicate:

Inspect the aquarium carefully and test the water.

Never use household air fresheners or cleaning chemicals to mask aquarium odours.

Aquarium Temperature Too High

High temperatures can reduce dissolved oxygen and stress fish.

Check:

If cooling is necessary, avoid sudden temperature changes.

Aquarium Temperature Too Low

If a tropical aquarium becomes too cold, check:

Use a separate thermometer to confirm the actual water temperature.

Filter Not Working

A failed filter should be addressed promptly.

Check:

Never run equipment dry unless the manufacturer specifically states that it is designed for this.

Filter Flow Is Weak

Reduced flow can be caused by:

Inspect the filter and clean appropriate components.

Avoid replacing all biological media unnecessarily.

Aquarium Heater Not Working

If the heater appears not to be maintaining temperature:

  1. Check the thermometer.
  2. Check the heater setting.
  3. Confirm the heater is powered.
  4. Inspect for visible damage.
  5. Check whether the aquarium temperature is actually changing.

Replace damaged equipment appropriately and follow manufacturer guidance.

Aquarium Lights Not Working

Check:

If plants begin deteriorating after a lighting failure, address the issue promptly.

CO₂ Problems

CO₂ systems require careful monitoring.

Potential problems include:

If fish show signs of distress, prioritise fish safety and investigate CO₂ immediately.

Fish Gasping in a CO₂ Aquarium

If fish begin gasping after CO₂ is introduced or increased, review the CO₂ system.

Increase appropriate gas exchange and investigate the cause.

Do not prioritise achieving maximum plant growth over fish welfare.

Aquarium Water Has a Film on the Surface

A surface film can reduce gas exchange.

Possible causes include:

Increasing appropriate surface agitation can help.

Review feeding and general maintenance as well.

Aquarium Has Excessive Algae

When algae becomes persistent, review the complete system.

Consider:

Avoid treating each algae outbreak as a completely separate problem.

Plants Turning Yellow

Yellow leaves can have several causes.

Possible factors include:

Look at new growth as well as older leaves to help determine what is happening.

Plants Melting

Some aquarium plants experience leaf loss after being introduced.

This can happen when plants transition from emersed growth to submerged growth.

New underwater leaves may eventually develop.

However, persistent deterioration can indicate unsuitable conditions.

Plants Not Growing

Poor plant growth can result from:

Check the complete growing environment rather than changing one factor blindly.

Shrimp Dying

If shrimp are dying unexpectedly, investigate:

Shrimp can be particularly sensitive to sudden changes.

Snails Dying

Investigate:

Some snail species also have specific mineral requirements for healthy shell development.

Sudden Fish Death

If a fish dies unexpectedly:

  1. Remove the fish.
  2. Check the remaining livestock.
  3. Test ammonia and nitrite.
  4. Check temperature.
  5. Review recent changes.
  6. Inspect equipment.
  7. Consider whether other fish show symptoms.

If multiple fish begin dying, treat the situation as urgent and investigate water quality immediately.

Ammonia Problems

Ammonia can be dangerous to fish.

Potential causes include:

Test the water and take appropriate corrective action.

Nitrite Problems

Nitrite can interfere with fish respiration and is particularly concerning during aquarium cycling or biological filtration failures.

Check:

Continue monitoring until the aquarium stabilises.

High Nitrate

Nitrate is generally less immediately toxic than ammonia or nitrite, but persistently elevated levels indicate that the aquarium’s waste-management system needs attention.

Potential causes include:

Review the overall maintenance routine.

Aquarium pH Problems

A sudden pH change can stress fish.

Before attempting to change pH, determine why it is changing.

Factors include:

Avoid making rapid pH adjustments simply to achieve a particular number.

Fish Fighting

Aggression can occur because of:

Provide appropriate space and hiding areas, and research species compatibility.

Aquarium Troubleshooting Golden Rule

Test before you treat.

Do not automatically add medication, chemicals, algae treatments or other products simply because something looks wrong.

Water testing and careful observation can often provide valuable clues.

Keep an Aquarium Journal

A simple aquarium journal can be extremely useful.

Record:

This makes it much easier to identify patterns.

When to Seek Professional Help

Consider professional advice when:

Professional Aquarium Troubleshooting From Aquassi Ltd

Aquassi Ltd can help identify aquarium problems and develop practical solutions.

Our services include:

We focus on identifying the underlying cause rather than simply treating the visible symptom.

A Healthy Aquarium Starts With Balance

Most aquarium problems become easier to manage when the fundamentals are right.

Maintain:

Good water quality

Appropriate filtration

Suitable lighting

Compatible livestock

Healthy plants

Responsible feeding

Regular maintenance

Stable conditions

Aquarium troubleshooting is not about reacting to every small change. It is about observing, testing, understanding and making informed adjustments.

Aquassi Ltd – professional aquascaping, aquarium design, fish care and aquarium maintenance.

Whether you are setting up your first aquarium or dealing with an established tank problem, Aquassi Ltd can help you create a healthier, more stable and beautiful aquatic environment.

Powered by
►
Necessary cookies enable essential site features like secure log-ins and consent preference adjustments. They do not store personal data.
None
►
Functional cookies support features like content sharing on social media, collecting feedback, and enabling third-party tools.
None
►
Analytical cookies track visitor interactions, providing insights on metrics like visitor count, bounce rate, and traffic sources.
None
►
Advertisement cookies deliver personalized ads based on your previous visits and analyze the effectiveness of ad campaigns.
None
Powered by