Splash filters and biofilters for garden ponds

⚙️ HOW SPRAY FILTERS AND BIOFILTERS WORK
1️⃣ Splash filters

Water is pumped through the filter material, which is moistened and splashed (flows over the surface or is sprayed through it).

It works on the principle of:

mechanical filtration - captures larger impurities, mud, leaves (I recommend inserting a drum filtration before such a filter).

biological filtration - beneficial bacteria settle on the filter medium, which break down toxic ammonia and nitrites.

Splashing increases the access of oxygen to the bacteria, thereby increasing the efficiency of biological filtration.

2️⃣ Biofilters

Biofilters are designed primarily for biological filtration of water.

Water flows through a medium where nitrifying bacteria live, which break down fish waste:

Ammonia (NH₃) → Nitrites (NO₂⁻) → Nitrates (NO₃⁻)

Biofilters can be internal or external, and are often combined with trickling filters for greater efficiency.

🏠 FILTER REQUIREMENTS
💧 Water

Clean or slightly polluted water

Biofilter works best at a water temperature of 15–28 °C

⚙️ Maintenance

Drip filters: regular cleaning of the mechanical part (sponges, grids)

Biofilters: no need to clean the bacteria too much, just remove larger impurities and maintain the water flow

Flow control - the correct flow ensures enough oxygen for the bacteria

🌞 Location and access to light

Filters can be placed in or out of the water

Drip filters outside the water - the water is dripped onto the medium, the bacteria are better oxygenated

🧠 "NATURE" OF FILTERS

Passive, undemanding devices that work continuously

Their effectiveness depends on proper maintenance, flow rate and filter size in relation to the volume of the pond

Sensitive to fish overload or polluted water

🧱 TYPES OF FILTERS
🌊 Drip filters

External drip filters – water is pumped from the pond and sprayed onto the filter medium

Internal sprayed filters – located inside the pond, less effective for large volumes

🌿 Biofilters

Filters with mechanical-biological media – combine the removal of larger impurities and biological filtration

Pure biological filters – designed only for nitrifying bacteria, water flows through the bio-medium

Overflow biofilters – water from the pond flows through the filter by gravity and is sprayed onto the medium

🩺 IMPACT ON THE HEALTH OF THE POND
POSITIVE

✔️ clean, transparent water
✔️ healthy fish without stress and diseases
✔️ stable pH and nitrite levels
✔️ reduced algae

NEGATIVE / PROBLEMS

❌ filter overload → accumulation of toxins
❌ filter contamination – reduced efficiency
❌ excessive cleaning of the biological part → destruction of bacteria
❌ inappropriate filter size → water quality reduction

⚖️ ADVANTAGES AND DISADVANTAGES
👍 ADVANTAGES

✅ effective biological and mechanical filtration
✅ reduces algae and dirt
✅ provides a stable and healthy ecosystem
✅ supports fish and plant health

👎 DISADVANTAGES

❌ need for regular maintenance and cleaning
❌ higher initial investment for larger ponds
❌ an incorrectly designed filter may be ineffective

🛒 HOW TO CHOOSE THE RIGHT ONE

Pond size - the filter must be sized for the water volume

Number and species of fish - more fish = more filter load

Filter type - a combination of a trickling and biofilter is often the most effective

Maintenance - whether you prefer simpler internal filters or powerful external ones

Material and quality - resistance to UV radiation and frost

📌 Tip: for ponds with a larger number of fish or koi ponds, trickling filters and external biofilters are practically essential for stable water quality.

🧭 PRACTICAL TIPS

Check and clean the mechanical part of the filter before the season

Never clean the entire medium at once - keep at least 1/3 of the bacteria

Regularly check the water flow and the spraying of the medium

Combine with plants - they also help remove nutrients and reduce the filter load

📌 SUMMARY

Spray filters and biofilters are the basis of a clean, healthy pond.

The right combination and maintenance:

keeps the water transparent,

ensures healthy fish,

reduces algae,

stabilizes the biological balance of the pond.

Without these filters, even an aesthetically beautiful pond would degrade very quickly and the fish would suffer.