- Prepare a documented fishless cycling process.
- Interpret ammonia, nitrite and nitrate together.
- Demonstrate capacity before gradual stocking.
01 / Establish a living process
Cycling develops a microbial community that converts ammonia through nitrite to nitrate. It requires wetted surface, oxygen, appropriate temperature and sufficient alkalinity. A new tank of clear water is not a functioning biofilter.
Use a fishless approach so establishment can be monitored without exposing fish to rising ammonia and nitrite. Select a known cycling product intended for the purpose and follow its concentration and dosing instructions. Household cleaners can contain surfactants or other additives and are not an interchangeable ammonia source.
Reading: Nitrification and Maintenance in Media Bed Aquaponics ↗ · Fish Health Management Considerations in Recirculating Aquaculture Systems—Part 1 ↗
02 / Prepare the test conditions
Commission water flow and aeration before dosing. Remove chlorine/chloramine with an appropriate method and verify the treated water. Install the full biological media inventory and maintain the temperature intended for startup.
Check test-kit units, range and expiration. TAN may be reported as nitrogen; nitrite may be reported as NO₂ or NO₂-N. Do not compare numbers from different reporting bases as though they were identical. Set up a daily log with pH, temperature, alkalinity and dosing.
- Measure baseline TAN, nitrite, nitrate, pH, temperature, alkalinity and oxygen.
- Add only the documented cycling product at its instructed dose to the measured system volume, with no fish present.
- Maintain flow and aeration, then measure on the product’s schedule and record the progression.
- Watch for ammonia clearance followed by nitrite clearance and nitrate formation; test kit limits matter.
- Repeat the documented challenge and clearance check rather than declaring success from one low sample.
- Stop artificial ammonia input before introducing fish; stock gradually within demonstrated capacity and continue close testing.
Reading: Ammonia in Aquatic Systems (FA16) ↗
03 / Read the sequence without a deadline
Ammonia may rise before the organisms processing it are established. Nitrite can then accumulate until the next conversion step keeps pace. Nitrate formation supports the interpretation but does not alone prove that both earlier compounds are being handled at the planned load.
Temperature, pH, oxygen and the inoculum affect the timeline. Do not promise a fixed number of days. A bottled inoculant or mature-media transfer can help only if appropriate viable organisms and conditions are present; imported media can also import disease.
Reading: Fish Health Management Considerations in Recirculating Aquaculture Systems—Part 1 ↗
04 / Troubleshoot a stalled cycle
If readings stop changing, verify the test method and dilution before adding more ammonia. Check dechlorination, oxygen, temperature, pH and alkalinity. An input well beyond the product’s instructions may inhibit progress rather than speed it.
If pH has fallen sharply while TAN remains high, do not make a large sudden upward correction. Higher pH can increase the toxic un-ionized ammonia fraction. Reconstruct conditions and use the cycling product and aquaculture guidance for a controlled correction.
| Observation | Check | Avoid |
|---|---|---|
| No detectable nitrogen change | Product concentration, kit method, chlorine and temperature | Repeated blind additions. |
| Nitrite persists | Oxygen, pH, time and load | Stocking because ammonia alone reads low. |
| One clear sample | Recent dilution and challenge history | Calling the system mature from a single result. |
| pH declines | Alkalinity and nitrification demand | Large unmeasured pH corrections. |
Reading: Ammonia in Aquatic Systems (FA16) ↗
Parts & buying criteria
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.
Supplier links can be added by the publisher. The criteria stand independently.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.
Supplier links can be added by the publisher. The criteria stand independently.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.
Supplier links can be added by the publisher. The criteria stand independently.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.
Supplier links can be added by the publisher. The criteria stand independently.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.
Supplier links can be added by the publisher. The criteria stand independently.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.
Supplier links can be added by the publisher. The criteria stand independently.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.
- 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 1 ↗
RAS treatment capacity and startup.
- University of Florida IFAS ExtensionAmmonia in Aquatic Systems (FA16) ↗
TAN, pH, temperature and fish response.
The next useful connections.
Water quality: pH, ammonia and alkalinity
Track the interacting measurements that govern fish, roots and nitrification.
Interactive tool · 6 min + guided practice →Cycling & water balanceSolids removal and biological filtration
Separate particle collection from dissolved nitrogen conversion and design maintenance access into both.
6 min + guided practice →