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<\/a>).<\/p>\n A settler<\/a> 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.<\/p>\n A filter drum<\/a> passes water through a rotating screen. Solids caught on the screen are washed off into a waste channel. Our standard is a 74 \u03bcm 316L screen, in PP box or stainless sinking types, from 10 to 600 m\u00b3\/h.<\/p>\n A finer screen is not always better. A 2025 trial on trout RAS found 45 \u03bcm gave better water quality than 70 \u03bcm, and 30 \u03bcm gave no further gain (DTU 2025<\/a>).<\/p>\n Fine particles and dissolved organics pass any screen. A skimmer protein<\/a> lifts them out as foam. It is standard in marine and shrimp systems and useful in dense freshwater ones, often paired with ozone.<\/p>\n An Biofilter MBBR<\/a> 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<\/a>).<\/p>\nSettlers<\/h3>\n
Filter drum<\/h3>\n
Fine solids and organics<\/h2>\n
Amonia<\/h2>\n
The usual order<\/h2>\n