Filtration systems for ponds and RAS

Why most pond filters fail to produce consistently clear water

The pond equipment market is still dominated by pressure filters — so-called ‘barrels’ with sponges and built-in UV. They look like a ready-made solution: a compact housing, claimed capacities of up to tens of cubic metres, and simple connection. This is precisely why they are most often chosen by owners of ornamental and koi ponds.

The problem is that such filters operate on a cumulative principle. All the debris — food residues, silt, organic matter — is not removed from the system but remains inside the sponges. After a short time, they begin to clog, and the filter’s efficiency drops sharply.

As a result, the system ceases to operate reliably. The flow weakens, circulation deteriorates, the water becomes cloudy, and the filter itself requires regular manual cleaning. After rinsing, the situation improves temporarily, but then the whole process repeats itself. This is a vicious cycle faced by most pond owners.

How pond filtration should actually work

A stable filtration system is based on a different principle — removing contaminants from the water as soon as they appear. This is exactly how drum filters and combined solutions used in modern ponds and RAS systems work.

Water passes through a screen; mechanical debris is trapped on the surface and automatically flushed into the drain. Contaminants do not accumulate inside the filter and do not affect its flow capacity. This allows the system to operate continuously, without a drop in flow and without the need for constant manual cleaning.

This approach ensures stable circulation, predictable water quality and reduces the load on the entire system. Filtration ceases to be a weak point and becomes the foundation of the pond’s operation.

CrawTec solutions for pond filtration

CrawTec filtration systems are designed from the outset as solutions for continuous operation, rather than as a temporary compromise. They are based on the principle of removing mechanical contaminants, which is used in recirculating aquaculture systems (RAS) and professional aquaculture.

This means a stable water flow, no accumulation of dirt inside the filter and minimal maintenance. The system is not dependent on when it was last cleaned and does not operate cyclically, unlike storage filters.

As a result, you get not just a filter, but a system that ensures clear water, stable circulation and predictable pond operation without constant intervention.