Aquarium Care Guide: Filtration, Water Quality, and Fish Behavior

A healthy aquarium is built on consistency, observation, and respect for aquatic life. Many problems faced by beginner and intermediate aquarists—such as stressed fish, unstable water, or unexplained losses—are usually caused by basic maintenance and environmental mistakes. This guide clearly separates the key topics every aquarist should understand to maintain a stable and ethical aquarium.

PWC: The Foundation of Aquarium Stability

In aquarism, PWC means Partial Water Change. It is one of the most essential practices in responsible fishkeeping and cannot be replaced by filtration alone.

A Partial Water Change consists of removing a portion of aquarium water (typically 10–40%) and replacing it with clean, treated water of similar temperature and parameters.

Most long-term aquarium problems stem from neglected, inconsistent, or improperly executed partial water changes.

Why Partial Water Changes Matter

Partial Water Changes perform several critical functions:

• Dilute accumulated toxins such as nitrates and dissolved organic waste
• Replenish essential minerals and trace elements
• Stabilize water chemistry over time
• Improve oxygenation and overall water quality

Unlike large or full water changes, PWCs correct water quality gradually while preserving beneficial bacteria and biological stability.

How Often PWCs Should Be Done

There is no universal rule, but common guidelines include:

• Lightly stocked aquariums: 10–20% weekly
• Moderately stocked aquariums: 20–30% weekly
• Heavily stocked or grow-out tanks: 30–40% weekly

Consistency is more important than volume. Small, regular changes are safer than large, infrequent ones.

Common PWC Mistakes to Avoid

• Skipping water changes because the water looks clear
• Performing large changes without matching temperature
• Forgetting dechlorinator when using tap water
• Over-vacuuming and disrupting substrate biology

Clear water does not mean clean water.

Disco fish in a home aquarium

Cleaning and Maintaining a Hang-On-Back (HOB) Filter

Hang-on-back filters are widely used, but incorrect cleaning can disrupt biological balance.

Proper Cleaning Guidelines

• Rinse filter media in old aquarium water
• Never use soap or untreated tap water
• Clean only when water flow is reduced

Preserving beneficial bacteria is more important than making the filter look clean.

What to Clean

• Mechanical sponge or floss: light rinse only
• Impeller and intake tube: monthly inspection and cleaning
• Biological media: disturb as little as possible

Changing Filter Media Safely

Replacing filter media incorrectly can cause ammonia and nitrite spikes.

Never replace all filter media at the same time.

Best Practices

• Replace only damaged or deteriorated mechanical media
• Stagger replacements over several weeks
• Prefer reusable sponges and ceramic biological media

Stable filtration supports long-term aquarium health.

Watching Temperature During Extreme Seasons

Fish rely entirely on water temperature to regulate their bodies.

Winter Risks

• Heater malfunction
• Sudden nighttime temperature drops

Summer Risks

• Overheating
• Reduced oxygen levels

Season	Main Risk	Prevention
Winter	Heater failure	Daily temperature checks
Summer	Overheating	Ventilation and increased aeration

Sudden temperature changes are more harmful than slightly imperfect temperatures.

A stable planted aquarium

Importance of an Adequate Aquarium Size

Tank size directly affects water stability and fish behavior.

Why Size Matters

• Waste accumulates faster in small volumes
• Aggression increases with limited space
• Temperature and pH fluctuate more easily

Always research adult fish size before choosing a tank.

How pH and GH Influence Fish Health

Water chemistry plays a critical role in long-term fish well-being.

pH

• Influences stress levels and immune response
• Rapid changes can cause physiological shock

GH (General Hardness)

• Affects osmoregulation and mineral balance
• Important for bone development and breeding

Stable parameters are safer than frequent adjustments.

Parameter	Primary Effect	Importance
pH	Stress control	Immune health
GH	Mineral balance	Growth and vitality

Understanding Fish Aggression

Aggression is usually caused by environmental conditions rather than inherent temperament.

Common Causes

• Overcrowding
• Incompatible species
• Lack of hiding places or territory

Prevention

• Choose compatible species
• Provide plants, caves, and visual barriers
• Avoid mixing territorial fish in small tanks

Early signs include fin damage, constant chasing, and prolonged hiding.

Final Thoughts on Responsible Fishkeeping

Successful aquariums depend on consistent partial water changes, stable filtration, controlled temperature, adequate space, and informed stocking choices. When these fundamentals are respected, aquariums become stable ecosystems rather than fragile systems.

Responsible aquarism prioritizes prevention, consistency, and animal welfare above all else.