Choosing a drum filter for aquaculture starts with two things: the water flow the filter must handle and the suspended solids carried in that water. The right choice also depends on the screen, backwashing system and the way the unit fits into your RAS. A model's advertised flow rate or micron rating alone cannot tell you whether it will work under your actual operating conditions.
For a new RAS, we would consider the filter alongside the treatment channels, pipework and operating water levels before the layout is finalized. For a retrofit, we start with the existing flow path, the civil work the site can accommodate and the water conditions. The aim is to find equipment that fits the project rather than force an unsuitable layout around a particular filter model. The sections below explain how we make that assessment.
Start With the Flow the Filter Must Actually Handle
The first question is not how much water your farm contains. It is how much water is expected to pass through this filter during operation.
A farm's total water volume does not establish its recirculation flow. Two systems with similar culture volumes can operate with different circulation arrangements. And even within one system, not all water necessarily travels through the same filtration unit. This is why we would look at the actual route through the mechanical filtration stage before settling on a particular filter model.
Check normal flow, peak flow and the flow route
Start with the design flow through the drum filter or filter group. If that figure is still an estimate, identify who will confirm it. Then consider whether the proposed operating plan includes a higher flow at certain stages, changes between operating modes or separate lines feeding several filters.
For example, a plant may divide its mechanical filtration flow between parallel units. That does not automatically mean every unit handles an equal share under all operating conditions. The pipework, water levels, controls and arrangements for isolating a unit can affect what each filter is actually asked to carry.
What does a rated flow actually mean?
We offer drum-filter models with different rated flow capacities, so we can use your planned circulation flow to narrow down the options. But the number on a model chart does not tell us exactly how a filter will perform on your site. Operating water levels, screen specification and solids loading can all affect the result.
Before using a rating as a final selection basis, we would want to confirm the specified screen, available water-level conditions and expected solids loading for the actual model. A filter that passes the required flow in one set of conditions should not automatically be assumed to handle the same flow in every installation.
Consider the Solids Load, Not Just the Water Flow
Water flow tells us how much water reaches the screen. It does not tell us how much material the screen will need to retain and wash away.
Consider two farms with similar circulation flow. If their species, feeding schedules and production stages differ, the suspended solids arriving at their filters may also differ. Feed particles, feces and other suspended material vary in amount and characteristics. Those differences can change how the screen loads during operation.
We would therefore discuss the expected production stage, fish or shrimp species, feeding conditions and where the filter receives its water. An existing farm may already have useful observations or water-quality records. A new project may only have planned biomass and feed assumptions. Either is a valid starting point, as long as the information is not presented as measured when it is only projected.
What if you do not have a TSS measurement?
Total suspended solids (TSS) is one way to describe the amount of suspended material in the water, but a single TSS number still does not describe every aspect of that material. Particle size and the way solids build up on a particular screen also matter.
If reliable TSS or particle-size data are unavailable, we can begin with the production plan and identify where a model-specific check or water sample would add value. We would not turn a feed-rate estimate into a guaranteed drum-filter capacity without a supported method and the relevant model data.
Choose the Screen as Part of the Whole Filter
A finer screen may retain different particles from a more open screen, but smaller openings do not automatically make the complete filter a better choice. Screen loading, available filtration area, operating water levels and backwashing all influence how the unit performs.
Both of our current drum-filter series use a 74 μm (200 mesh) screen as standard. But screen aperture is only one part of the selection; it does not mean a filter will completely capture particles of a certain size under every operating condition. For a general explanation of screen openings and the filtration process, see What Is an Aquaculture Drum Filter?.
Compare screen options against the actual water
Our first consideration would be the type of solids you need to manage and the screen specification offered with the selected unit. We would then check how that screen affects the equipment's flow and backwash requirements under the proposed conditions.
Aquaculture engineering research has also identified screen aperture, suspended-solids characteristics and hydraulic operating conditions as relevant variables in microscreen drum-filter selection. That supports evaluating the complete operating situation, rather than treating the micron number as a stand-alone result. It does not replace test data for our specific models or establish what one of our filters will achieve in a particular installation.
We can cover the differences between 60 μm and 80 μm screens separately. Whether either is available must be confirmed for the specific model and supply configuration; we would not present them as currently confirmed standard options.
Compare Drum Filter Configurations Against Your Site
Our two current platforms are the Box Type PP Drum Filter and the Sinking Type Stainless Steel Drum Filter. They differ not only in housing material, but also in how water enters the unit, the civil works required for installation and the materials exposed to the water.
Looking at our current model range, the PP box-type filters are rated at 30–300 m³/h, while the sinking stainless steel models are rated at 100–600 m³/h. There is some overlap. We still need to consider the actual operating water levels, solids loading and conditions for the specific model; the rated flow alone does not decide which filter fits your project. Here is how we compare the two designs.
When a box-type PP filter is worth evaluating
For relatively small flows entering through pipework, we often assess a PP box-type unit first. It does not rely on the dedicated inlet channel required by a sinking unit, and our series offers floor-mounted, recessed and elevated installation options. We still have to check pipe size, inlet and outlet elevations and available hydraulic head.
At an existing farm with a hardened floor, or where civil works and approvals are difficult, a pipe-fed arrangement may reduce the site work needed. We would confirm that the existing flow route can serve the proposed unit and that there is enough access to maintain the screen and backwashing components.
In brackish or marine aquaculture, we also tend to consider the PP housing first. Unlike stainless steel, the PP body does not undergo chloride-driven metallic pitting or crevice corrosion. Our current PP box-type filters still use a 316L stainless steel screen. So, for brackish or seawater projects, we also check the screen, fasteners, fittings and seals to make sure the parts in contact with water suit the actual salinity and operating conditions. A saltwater-resistant PP housing does not make the entire machine immune to corrosion or maintenance issues.
When a sinking stainless steel filter is worth evaluating
For a new freshwater RAS designed around a higher circulation flow, we would consider a sinking filter when the treatment channel can be incorporated into the civil works. Water can enter directly from a wider channel rather than mainly through the inlet pipe used for a box unit. This can suit a channel-based high-flow layout, but the inlet arrangement alone does not establish the actual processing capacity.
The site must be able to accommodate a filter pit or channel and a suitable operating water-level difference, so water can reach the recessed unit by gravity under the proposed hydraulic design. We would check excavation depth, channel dimensions, upstream and downstream levels, the backwash-waste route and access for lifting or servicing the equipment before civil work begins. A retrofit with an existing suitable channel can also be a candidate. Where the floor is already hardened and cannot be opened, it would be difficult to justify the sinking configuration on its rated flow alone.
Our sinking series uses 304/316 stainless steel construction. In freshwater it can be evaluated against the flow and channel conditions. In brackish or marine applications, material compatibility and long-term corrosion deserve closer scrutiny. Even 316 stainless steel is not immune to prolonged seawater exposure, particularly at crevices, joints and fasteners.
Check Backwashing and Waste Discharge Before Ordering
A drum filter does more than retain solids on a screen. It also needs to remove those solids from the filter without interrupting the intended water-treatment process.
Take the automatic backwashing arrangement shown for our filters: as solids build up and restrict water movement through the screen, the control system can activate drum rotation and spray cleaning. The collected waste then leaves through the discharge route. We explain that sequence in our drum filter overview; here, the more useful question is whether your site can support the process.
For selection, we would focus less on repeating how the mechanism works and more on whether your site can support it.
Water supply and the cleaning system
Confirm the cleaning-water supply and pressure required by the proposed model, along with its pump and control arrangement. Those requirements should come from the actual equipment specification. We should not infer backwash consumption or cleaning intervals from the fact that a unit has automatic backwashing.
Backwash activity can change as screen loading and operating conditions change. Frequent cleaning deserves investigation, but by itself does not establish that a filter is undersized or defective.
Where will the captured waste go?
The waste discharge route deserves as much attention as the clean-water outlet. Confirm whether the treatment room has a suitable drain, channel or collection system for the discharged solids and cleaning water. Consider the intended waste-handling plan and whether the drain can be accessed for inspection.
Before comparing quotations, ask whether the backwash pump, relevant controls, connections and any required site piping are included or assigned to another party.
Confirm Hydraulic Integration and Maintenance Access
A drum filter can look suitable in a model table and still be difficult to install correctly within a particular RAS layout.
We would place the proposed filter on the actual treatment drawing and trace the water through its inlet and outlet. For a sinking filter, check the channel depth, available gravity-flow head and maintenance access before civil work begins. For a PP box unit, confirm the existing pipe connections and inlet/outlet elevations can support the installation. Operating water levels, available space and what happens during backwashing must still be considered.
If several filters operate in parallel, the layout should also make clear how flows are distributed and how a unit can be accessed or isolated for service, where that capability is required by the project. Final hydraulic checks and any pump or pipe sizing belong to the engineering design, not a generic article formula.
Make sure the filter can be serviced where it is installed
Check that staff can reach the screen, spray nozzles, sensors, drive components and waste channel in the proposed position. Space on the installation drawing should include the access needed to inspect or replace parts, not just the overall equipment dimensions.
If the equipment is installed below floor level or in a channel, consider the practical route for lifting or removing components. Those details can affect civil works, equipment-room layout and maintenance arrangements before any filter is ordered.
Drum-filter connections also need to fit the complete RAS system design. The filter is one stage of the water-treatment process; selecting it independently does not confirm that the complete flow path will work as intended.
Compare Suppliers' Quotations on the Same Basis
If two suppliers recommend different drum-filter models, the useful question is not only which has the lower price. It is what each quotation assumes the filter will handle, and what the quoted package actually includes.
| What to compare | What the proposal should make clear |
|---|---|
| Design flow | Flow through the proposed filter or filter group, including relevant operating and peak conditions |
| Rated conditions | Screen specification and the hydraulic and solids-loading assumptions behind the stated capacity |
| Solids to be handled | Available TSS or particle data, or clearly labeled production and feeding assumptions |
| Filter construction | Body and screen materials, wetted components, exposure limitations and exact offered configuration |
| Backwashing | Water supply, required pressure, pump/control scope, waste discharge and any assumptions about operation |
| Installation | Arrangement, equipment dimensions, water levels, inlet/outlet locations, pipe and channel interfaces |
| Maintenance | Access to screen, nozzles and moving parts; replacement parts and relevant documentation |
| Scope and handover | Drawings, installation responsibilities, testing or commissioning scope, exclusions and warranty terms |
A more expensive filter is not automatically the safer choice, and a lower quotation is not automatically better value. Compare the offered conditions and responsibilities before treating two prices as equivalent.
If a supplier proposes a different platform or rating, ask what specific project condition led to that recommendation. The answer should help you understand the tradeoff rather than leave you comparing model-chart numbers alone.
How to Start a Drum Filter Selection Discussion With Us
You can start with what you already know. The most useful first details are your application, approximate flow through mechanical filtration, species and production stage, freshwater or marine conditions, and any limits imposed by the site or existing treatment area.
If you have a drawing, feeding plan or water-quality results, those can help us review the options. If you do not, explain what is already decided and what is still being estimated. We can use that information to discuss likely filter configurations and identify the model-specific data needed for a recommendation.
The goal is not to complete an engineering specification before your first inquiry. It is to make the next discussion productive and avoid selecting a filter on an assumption that has not been checked.
Frequently Asked Questions About Drum Filter Selection
Can I size a drum filter by total tank water volume?
Not by water volume alone. The flow routed through the unit and the solids it must handle are more directly relevant. Total system volume can provide context, but it does not establish a filter's required flow capacity or screen loading.
Is a finer micron screen always better?
No. A finer screen can change which particles are retained, but it can also affect how the screen loads, the available flow and the backwash requirements. Evaluate the screen within the complete filter under your expected operating conditions.
How are flow rate and solids loading related?
Flow describes the volume of water passing through the filter over time. Solids loading describes the particulate material carried by that water. Two systems with the same flow may expose a filter to different solids conditions and therefore require different checks before a model is selected.
Which is more suitable: a PP box unit or a sinking stainless steel filter?
There is no fixed answer for every project. We compare the inlet arrangement, available civil works, water conditions and operating load; the two configurations are discussed in detail above. Before selecting a model, we still need to confirm the water levels, solids loading and materials throughout the wetted assembly.
What if I don't know the solids loading yet?
You can still begin the selection discussion. Share the intended species, production stage, feeding assumptions and available system information. Mark any estimates clearly; then identify whether water testing or model-specific evidence is needed before final selection.
Reference
Dolan, E., Murphy, N., & O'Hehir, M. (2013). Factors influencing optimal micro-screen drum filter selection for recirculating aquaculture systems. Aquacultural Engineering, 56, 42–50. https://doi.org/10.1016/j.aquaeng.2013.04.005 — External research supporting the importance of screen, solids and hydraulic variables; not performance validation for our specific equipment.
Let’s Discuss Your Drum Filter Options
Planning a new RAS or trying to find a better fit for an existing treatment line? Tell us the flow you expect to filter, the type of aquaculture system and any installation constraints you already know. We can discuss which drum-filter configurations deserve a closer look and what needs confirming before choosing a specific model.
Talk with us about your drum filter requirements. You can start with estimates or an early-stage layout; a complete technical package is not required for the first conversation.