- Distinguish particle capture from dissolved nitrogen conversion.
- Compare filter ratings on a consistent loading basis.
- Use measured flow and commissioning records to assess an installation.
01 / Separate two jobs in the water path
A mechanical separator removes particles such as uneaten feed and fish waste from the circulating water. A biological filter supports organisms that convert dissolved ammonia through nitrite to nitrate. Capturing visible dirt does not prove ammonia conversion, and a large biological surface does not automatically remove accumulated solids. SRAC 454 describes these functions within the aquaponic treatment train.
Walk the installed loop and identify where each job occurs. In a media bed, some functions can share a physical location, but that creates shared maintenance and loading constraints. In the teaching model, a separator and a biofilter appear as distinct components so the reader can inspect the difference. The model is not an instruction that every installation needs those exact vessels.
Reading: Aquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗
02 / Compare separators by capture and service
Start with the waste you need to remove and the actual flow that passes through the unit. Ask how particles enter, where captured material collects, how it leaves the system and what happens when the collector is full. A device that looks clear immediately after cleaning still needs an operating routine that prevents waste accumulation between services.
A settling vessel relies on particle behavior and the flow pattern through it. A screen or pad relies on the stated opening or material and can obstruct flow as it loads. An automated filter also needs a dependable cleaning process and a plan for loss of power or wash water. These are selection questions, not a ranking of particular products. Request performance information under conditions comparable to your system.
| Ask the supplier | Why it changes the purchase |
|---|---|
| What inlet flow and particle conditions were tested? | A label capacity may describe a different installation. |
| How is captured waste removed? | Cleaning must not send the waste straight back to fish. |
| What happens when the unit blocks? | Overflow, bypass and alarms need a planned response. |
| What are consumable and wash-water requirements? | Purchase price omits recurring operation. |
| Can the unit be isolated and serviced? | Maintenance access determines whether the routine is practical. |
03 / Ask what a biological capacity rating means
UF/IFAS explains that nitrifying organisms require oxygen and alkalinity and that a new biofilter takes time to establish. A new bag of media is not equivalent to a functioning mature filter. Species, feed load, temperature, pH, oxygen, flow and fouling change the conditions under which a capacity claim may apply. Avoid purchasing on nominal tank volume alone.
Ask whether the published capacity means grams of TAN-nitrogen removed per day, a particular feed input per day, or merely a marketing tank size. Record the test temperature, inlet and outlet concentrations, media fill, aeration, flow and startup assumptions where supplied. Surface area per litre can help describe media, but accessible, functioning biological surface under the installed conditions is the relevant issue. Do not compare incompatible rating bases as if they were the same measurement.
Reading: Ammonia in Aquatic Systems (FA16) ↗
04 / Use simple hydraulic arithmetic carefully
Nominal residence time equals the water volume in a vessel divided by the flow through it. An illustrative 30 L water inventory receiving 900 L/hour gives 30/900 hours, or two minutes. This is only an inventory-equivalent time: real flow can short-circuit, mix or bypass portions of the vessel. It does not prove how much ammonia is removed or which particles settle.
Use the actual water inventory after allowing for media and operating levels, and measure installed flow instead of using a pump’s maximum label rating. Record whether the entire system flow or only a side stream passes through the unit. If a branch changes, recalculate that branch’s nominal residence time and investigate the treatment result with measurements. A mathematically tidy turnover figure cannot replace testing.
FIELD QUESTIONTwo filters each hold 30 L, but one sees 900 L/hour and the other 1,800 L/hour. Are their nominal residence times the same?
No. The first is two minutes and the second one minute. Neither number by itself establishes waste capture or nitrification performance; their real flow patterns and operating evidence still matter.
05 / Buy against an acceptance record
Before installation, agree what can be checked: leak-free operation, the service procedure, water and air delivery, and water-quality results under a documented loading plan. Establish the biological process before exposing fish to an unproven capacity. The cycling chapter explains what to record; readiness depends on observed conversion and water conditions, not just days elapsed.
During operation, log feed, cleaning, flow, oxygen, pH, alkalinity, TAN and nitrite as the system plan requires. Clean according to the component’s instructions without treating biological media as an inert surface to sterilize during normal operation. After a chemical treatment or major maintenance change, verify that conversion remains effective. If a quoted filter cannot be explained in these terms, obtain clarification before paying for a larger model.
Reading: Nitrification and Maintenance in Media Bed Aquaponics ↗ · Fish Health Management Considerations in Recirculating Aquaculture Systems—Part 3 ↗
Parts & buying criteria
Build your own parts & cost worksheet →
Showing aquaponic raft system. Quantities describe the teaching model. Specify real working volume, support, fittings and instruments for your installation.
01Fish tank1 · illustrated quantity+
Houses fish and receives the pumped return. Feed is an input to this living system.
Inspect: The fish are generic silhouettes, with no species or stocking-rate recommendation. Cutaway reveals the tank interior.
Maintain: Observe behavior and feeding response; keep a record of water tests and changes.
Smooth accessible tank, secure cover and species-appropriate volume determined by an aquaculture design.
Check size, materials and operating conditions with your chosen supplier before ordering.02Solids separator1 · illustrated quantity+
Intercepts settleable waste before it accumulates in later treatment and growing components.
Inspect: Open the front of the vessel. Brown particles beneath the central baffle represent collected waste, not a settling simulation.
Maintain: Inspect accumulation and remove it on an observation-based schedule without flushing it into the growing bed.
Accessible waste drain, removable internals and a design matched to expected solids and flow.
Check size, materials and operating conditions with your chosen supplier before ordering.03Biological filter1 · illustrated quantity+
Provides wetted surface for nitrifying organisms. This teaching layout shows a separate biofilter.
Inspect: The blue carriers indicate surface area; cyan flow does not measure nitrification or oxygen availability.
Maintain: Protect the established community during service. Verify nitrogen readings before and after changing loading or equipment.
Media and aeration matched to the intended feed load, water conditions and an independently reviewed design.
Check size, materials and operating conditions with your chosen supplier before ordering.04Raft growing bed1 · illustrated quantity+
Holds plants above water after solids handling and biofiltration. Roots hang below the raft.
Inspect: Compare the depth of this growing section with the shallow channels in the hydroponic lesson.
Maintain: Keep drains accessible and inspect root congestion. Remove crop debris without sending it downstream.
Cleanable bed, supported raft, access to drains and a root-zone aeration plan.
Check size, materials and operating conditions with your chosen supplier before ordering.05Sump & return pump1 · illustrated quantity+
Collects gravity drainage and pumps water to the fish tank, closing this particular circuit.
Inspect: This is the lowest collection point. The tank, filters and bed have progressively lower illustrative water levels.
Maintain: Check sump level, intake and leaks. Test whether drainage can be contained when power stops.
Usable reserve volume, pump service access, level protection and verified delivery at the required head.
Check size, materials and operating conditions with your chosen supplier before ordering.06Air supply1 · illustrated quantity+
A separate air pump supplies diffusers to the fish tank, biofilter and growing bed.
Inspect: White bubbles indicate air delivery only; bubble count is not a dissolved-oxygen reading.
Maintain: Check air lines, diffusers and backup arrangements. Verify oxygen with suitable measurement.
Airflow at operating depth, compatible diffusers and resilience reviewed for the living load.
Check size, materials and operating conditions with your chosen supplier before ordering.Evidence beside the lesson.
Source checks: September 2026. The geometry, inspection exercises and worksheets are original teaching material. The named organizations have not endorsed or reviewed this site.
Published recipe rates and planning ranges retain their source context. Calculator equations are accounting tools; they do not predict uptake, yield, toxicity or safe stocking. Model dimensions, water speeds, roots and fish counts are illustrative. Verify species, crop, source water and product labels for a real system.
- Southern Regional Aquaculture Center · hosted by OSU ExtensionAquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗
Tank-to-treatment-to-growing-to-sump layout and production tradeoffs.
- University of Florida IFAS ExtensionAmmonia in Aquatic Systems (FA16) ↗
TAN, pH, temperature and fish response.
- Oklahoma State University ExtensionNitrification and Maintenance in Media Bed Aquaponics ↗
Biofilter establishment, nitrogen testing and maintenance.
- University of Florida IFAS ExtensionFish Health Management Considerations in Recirculating Aquaculture Systems—Part 3 ↗
Biosecurity, quarantine, health monitoring and diagnosis.
The next useful connections.
Media-bed aquaponics: grow without hiding the waste
Design an accessible aggregate bed, verify flood and drain behavior and preserve its biological function.
6 min + guided practice →Cycling & water balanceFishless cycling: prove the biofilter works
Establish nitrification with a known input and repeated measurements before stocking.
6 min + guided practice →Cycling & water balanceWater quality: pH, ammonia and alkalinity
Track the interacting measurements that govern fish, roots and nitrification.
Interactive tool · 6 min + guided practice →Cycling & water balanceAmmonia spikes in aquaponics: confirm the reading and trace the cause
Read total ammonia with temperature, pH and its reporting basis. Restore failed system functions, reduce the immediate load and document a response before making chemical changes.
6 min + guided practice →Operation & resilienceAquaponics system planner: equipment, operating costs and commissioning
Prepare a purchasing worksheet for the complete fish-to-plant loop. Separate equipment costs from biological capacity, and include the work and reserves that protect a living system.
Interactive tool · 6 min + guided practice →