Aquaculture filtration: solids, organics and ammonia

Remove solids early

Solids break down in the water. The longer they stay, the more they turn into fine particles and ammonia, and the more oxygen they use. Fast removal protects every stage after it. In a DTU comparison, systems with drum filters had over 60% less particles, particulate BOD and particulate COD than systems without, and about half the microbial activity in the water (DTU).

Settlers

A settler slows the water so heavy particles drop out. It suits systems with a high solids load and cuts the work left for the drum filter.

Drum filters

A drum filter passes water through a rotating screen. Solids caught on the screen are washed off into a waste channel. Our standard is a 74 μm 316L screen, in PP box or stainless sinking types, from 10 to 600 m³/h.

A finer screen is not always better. A 2025 trial on trout RAS found 45 μm gave better water quality than 70 μm, and 30 μm gave no further gain (DTU 2025).

Fine solids and organics

Fine particles and dissolved organics pass any screen. A protein skimmer lifts them out as foam. It is standard in marine and shrimp systems and useful in dense freshwater ones, often paired with ozone.

Ammonia

An MBBR biofilter grows nitrifying bacteria on moving K5 media. They convert ammonia to nitrite and then nitrate. The biofilter is sized on peak daily feed, not tank volume. Poor solids removal cuts its capacity: in a yellow perch trial comparing three biofilter types, all removed less ammonia than expected because of a high organic load (Virginia Tech).

The usual order

• Tank drains
• Settler, where solids load is high
• Drum filter
• Protein skimmer, often on a side stream
• MBBR biofilter
• Degassing, oxygen and UV before the water returns

See the filtration overview, or send your flow and feed and we size the whole line.