- Compare documented suitability, geometry and access before price.
- Calculate and verify working water inventory.
- Separate tank volume from support loads and biological carrying capacity.
Gross volume calculator
Gross litres = internal length × width × actual water depth (m) × 1,000.
Gross water volume (L): 180
Rectangular geometry before displacement by media, plants, pipes and equipment. Calibrate level marks by measured filling and add connected tanks, beds and plumbing to the inventory used for concentration calculations. The dimensions are an illustrative example, not a recommended tank size.
01 / Buy a vessel for the actual use
Start with documentation of the material and its intended use with the water, fish and growing conditions you plan. Ask the manufacturer about the tank, fittings, sealants, liner, outdoor exposure and cleaning products together. A recycling symbol identifies a resin family; it is not a complete suitability assessment of the finished vessel or its previous contents.
For a reused container, obtain a credible history before considering it. Unknown contents, residues, coatings or structural damage are reasons to reject a bargain. Washing does not establish that an unknown chemical has been removed or that a weathered vessel can support a permanent installation. Compare a documented new tank with the full preparation, uncertainty and service cost of a reused one.
02 / Compare circulation and cleaning access
Rutgers’ aquaponics introduction favors circular, oval or multisided tanks for circulation and solids collection, while recommending rounded edges for rectangular vessels. That is a useful design consideration, not a claim that any circular tank cleans itself. The inlet, drain, fish behavior, actual flow and accumulated solids still determine what happens in the installed system.
Before buying, draw the service route. Can you see the fish, remove uneaten feed, inspect the screen, reach the drain and clean the bottom without dismantling the plant bed? Can a fish be caught without prolonged chasing or sharp surfaces? Can the lid or net be removed by one operator? Do not trade necessary access for the largest advertised water volume that fits a corner.
| Option | Questions before purchase |
|---|---|
| Round tank | Can the inlet, drain and screen support the intended flow and cleaning routine? |
| Rectangular tank | Are corners accessible and flow distribution demonstrated? |
| Lined structure | Who specifies the support, liner compatibility and protected edges? |
| Reused container | Are previous contents and structural condition documented? |
| Any tank | Are fish observation, catching, drainage and operator access practical? |
03 / Measure working volume, not label capacity
A tank’s capacity at the rim is different from its normal water inventory. Leave the freeboard, drains, covers and containment specified for the design. For a rectangular vessel with straight internal walls, gross water volume in litres is internal length × internal width × water depth in metres × 1,000. This geometric estimate excludes displacement by objects and any sloping or curved walls.
An example with internal dimensions 1.2 m × 0.8 m and 0.5 m water depth contains a gross 480 L. Filling to 0.6 m would give 576 L, a 96 L difference. Neither is an instruction to use those depths. A measured fill using a dependable volume meter or known containers is a better inventory check when the vessel has irregular geometry. Mark normal operating and pump-off levels after commissioning.
FIELD QUESTIONA seller calls a vessel a 600 L tank, but its measured operating inventory is 480 L. Which value belongs in a dilution calculation?
Use the actual relevant water inventory, including connected vessels where the calculation assumes the whole loop is mixed. A label capacity does not establish how much water is present during operation.
04 / Include the support and fault cases
At ordinary growing temperatures, a litre of freshwater has a mass close to one kilogram. The illustrative 480 L inventory therefore represents about 480 kg of water before the vessel, fish, fittings or any supported structure are included. This simple mass estimate is not a floor-load certification. Feet, frames and uneven ground can concentrate the load; support design must account for the real structure and local conditions.
Plan what happens if a return blocks, a siphon continues after power loss or a drain fitting leaks. Verify that pump-off drain-back fits within available storage. Use screens and covers suited to the species while preserving inspection and the required gas exchange. Rutgers discusses containment covers and the need not to seal the tank completely. Keep mains connections away from the water and use the protection and installation required by local electrical rules.
05 / Do not buy a fish load from a tank label
The tank is only one part of carrying capacity. The planned species and mature size must fit the containment, while feed input must remain within demonstrated oxygen, filtration and waste-handling capacity. Additional water can buffer some concentration changes, but it does not automatically supply oxygen or establish a biofilter. Use the fish and feeding chapters to develop and verify those separate requirements.
Ask for a quotation that separates the vessel, stand or support, drain, screens, cover, plumbing connections and delivery. Check doorways and the route to the final location. Add each accepted item to the parts planner, keep missing prices visible, then commission the complete water path before scheduling a fish shipment. The best-value tank is the one you can safely install, operate and service under the documented design.
Reading: Aquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗
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.
- Rutgers New Jersey Agricultural Experiment Station Cooperative ExtensionIntroduction to Aquaponics Systems (FS1351) ↗
Tank shape, circulation, solids collection, covers and accessible mechanical/biological treatment. Published tank-to-fish and filter-volume heuristics are not used as universal sizing rules in this guide.
- 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.
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 →Fish & feedingFeeding, biomass and stocking
Use fish mass and actual feed intake as operating inputs, with capacity checked independently.
Interactive tool · 6 min + guided practice →Operation & resilienceOxygen and outage resilience
Measure oxygen where it matters and rehearse a recovery plan before fish depend on it.
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 →ComparisonsMedia bed, raft or decoupled: choose by treatment and service
Choose an aggregate bed, a raft trough or a separated plant loop by where solids and nitrification happen, what the published depths and ratios imply, and what each demands when you service it or the pump stops.
8 min + guided practice →