- Match a fish to measured seasonal water temperature, not a hoped-for one.
- Size the direction of the heating or chilling burden before buying stock.
- Carry the choice through oxygen, legality, seedstock and the plant side.
Energy cost calculator
kWh = watts × hours/day × days ÷ 1,000. Cost = kWh × your tariff.
Energy (kWh): 43.2; Energy cost (your currency): 6.48
One device at constant power. Add other devices, duty cycles and fixed charges separately. Price is an illustrative input, not a market quote.
01 / Start from the water you can hold
The fish-selection chapter compares six groups by published bands. This guide takes the three food fish most often weighed against each other and asks which your building can hold inside its band all year, and what the other months cost. Log water temperature at the tank through the coldest and warmest weeks first; an outbuilding, a greenhouse and an outdoor sump settle differently under the same weather.
OSU HLA-6721 Table 3 supplies the planning bands: optimal 74–80°F for tilapia, 55–65°F for trout and 75–85°F for catfish, inside temperature ranges of 60–90, 35–68 and 35–95°F. NMSU CR680 gives 81–85°F for maximum tilapia growth and says growth slows dramatically below 70°F; SRAC 283 says tilapia generally stop feeding below 63°F. SRAC 180 gives optimum channel catfish growth at about 85°F. SRAC 223 gives 55–65°F as the trout optimum and says that above 68°F a trout’s digestive system does not use nutrients well. These figures answer different questions and stay separate rather than averaged.
Reading: Aquaponics (HLA-6721) ↗ · Important Water Quality Parameters in Aquaponics Systems (CR680) ↗ · Tilapia: Life History and Biology (SRAC 283) ↗ · Channel Catfish: Life History and Biology (SRAC 180) ↗ · Trout Production: Feeds and Feeding Methods (SRAC 223) ↗
02 / Compare the three
Each cell is that source’s statement in its context, not a specification for your tank. The SRAC sheets describe rainbow trout, channel catfish and mainly Nile, blue and Mozambique tilapia; the hatchery’s guidance for the exact stock governs.
| Criterion | Tilapia | Trout | Channel catfish |
|---|---|---|---|
| Planning band (OSU Table 3) | Optimal 74–80°F; range 60–90°F | Optimal 55–65°F; range 35–68°F | Optimal 75–85°F; range 35–95°F |
| Cold side | SRAC 283: feeding stops below 63°F; lethal 50–52°F for most species (blue tilapia to about 48°F) | The design condition; SRAC 223: restrict feeding below 40°F | SRAC 180: metabolic rate halves per 18°F drop and appetite falls with it |
| Warm side | SRAC 282: needs vigorous aeration | SRAC 223: above 68°F feed is used poorly | Inside its band to 85°F |
| Oxygen need (OSU Table 3) | Low | High | Low |
| Oxygen figure in a source | NMSU: about 5 ppm for warmwater fish, and hold 5 ppm or higher in aquaponics; tilapia tolerate less at a growth cost | NMSU: about 6.5 ppm; SRAC 222: cut loading below 6 ppm at outflow | SRAC 180: growth reduced below 4 ppm; lethal about 1 ppm |
| Mature size, time, diet (OSU Table 3) | 1.5 lb, 9–12 months, omnivore | 0.8 lb, 12 months, carnivore | 1.25 lb, 12–18 months, omnivore |
| Seasonal energy problem (original) | Heating in the cool season | Chilling when summer water passes 68°F | Heating for growth; survives cool unheated |
| Legal and seedstock | SRAC 283: many states restrict it as non-indigenous | Cold-water hatchery supply | Verify locally |
Reading: Aquaponics (HLA-6721) ↗ · Important Water Quality Parameters in Aquaponics Systems (CR680) ↗ · Tilapia: Life History and Biology (SRAC 283) ↗ · Tank Culture of Tilapia (SRAC 282) ↗ · Channel Catfish: Life History and Biology (SRAC 180) ↗ · Trout Farming: Carrying Capacity and Inventory Management (SRAC 222) ↗ · Trout Production: Feeds and Feeding Methods (SRAC 223) ↗
03 / Oxygen changes the answer
NMSU CR680 states that the warmer the water, the less oxygen it holds. Trout get more oxygen from the cold water they need; tilapia and catfish need less but their warm water holds less. SRAC 282 states that vigorous aeration is necessary in warm tilapia water and that it re-suspends and fractures solids, so pair aeration with prompt solids removal.
For trout, SRAC 222 names dissolved oxygen as normally the more critical of its two limiting factors in its raceway context and says loadings should be decreased when outflow dissolved oxygen drops below 6 ppm; rehearse the outage plan against that figure, not a generic 5 ppm. SRAC 283’s note that tilapia survive dawn oxygen below 0.3 mg/L describes pond tolerance, not an operating level.
Reading: Important Water Quality Parameters in Aquaponics Systems (CR680) ↗ · Tank Culture of Tilapia (SRAC 282) ↗ · Trout Farming: Carrying Capacity and Inventory Management (SRAC 222) ↗ · Tilapia: Life History and Biology (SRAC 283) ↗
04 / The energy bill points both ways
Tilapia in a temperate climate means heating through the cool season. Trout in the same building means chilling through summer, since SRAC 223 says trout use feed poorly above 68°F. Catfish sit between: OSU’s 35–95°F range covers an unheated cool season, but SRAC 180 says metabolic rate halves per 18°F drop and appetite falls with it, so expect little growth until the water warms. SRAC 282 says tank culture of tilapia can have higher labor and energy costs for pumping and heating water than pond methods, and that warming large volumes of incoming water is generally not economically feasible without geothermal or low-cost waste heat. Insulate and cover tank and sump, and keep loop volume no larger than needed.
One calculation is safe at home. Water’s specific heat is about 4.19 kJ per kg per °C, so lifting 1,000 L (about 1,000 kg) by 8.3°C (15°F) takes 1,000 × 4.19 × 8.3 ≈ 34,800 kJ, about 9.7 kWh, once. The ongoing input is the heat lost through walls, evaporation and ventilation, so meter the heater for a week and enter watts, hours, days and tariff in the energy calculator. A chiller’s draw is not the heat it removes; use the nameplate and a measured duty cycle.
FIELD QUESTIONA 1,000 L tank in an unheated outbuilding settles at 60°F in January. Which fish is inside its OSU band untouched, and what does lifting the water to 75°F for tilapia take, once?
Only trout: 60°F is inside 55–65°F and below the 74–80°F tilapia and 75–85°F catfish bands; at 60°F NMSU says tilapia growth has slowed dramatically and SRAC 283 says feeding has stopped. Lifting 1,000 kg by 8.3°C takes 1,000 × 4.19 × 8.3 ≈ 34,800 kJ, about 9.7 kWh, once; holding it costs whatever the tank loses. Then ask what the building does in July, which decides whether trout survive the other half of the year.
Reading: Tank Culture of Tilapia (SRAC 282) ↗ · Channel Catfish: Life History and Biology (SRAC 180) ↗ · Trout Production: Feeds and Feeding Methods (SRAC 223) ↗ · Aquaponics (HLA-6721) ↗
05 / Legality, seedstock and quarantine
OSU HLA-6721 lists state laws among the factors in choosing fish, noting that some states restrict certain species. SRAC 283 is specific about tilapia: native only to Africa, treated by many U.S. states as exotic or non-indigenous with restricted transport and culture, so check with state game and fish or natural-resources agencies or Extension fisheries specialists. SRAC 5007 gives the same instruction for aquaponics generally. Nothing here is a legal statement about your location.
Seedstock follows climate. Trout fingerlings come from cold-water hatcheries and must arrive cold. Tilapia sold for aquaponics may be mixed-sex, and SRAC 5007 notes they reproduce volitionally and frequently at acceptable temperatures, so plan for fry. UF/IFAS FA101 describes quarantine as isolation for 1–8 weeks depending on species, diseases of concern, system and prior testing.
- Record water temperature through the coldest and warmest weeks and note its distance from each OSU band.
- Strike any species whose band needs continuous heating or chilling you have not priced from a measured duty cycle.
- Confirm with the state agency or an Extension fisheries specialist that the remaining species may be kept, moved and sold where you are.
- Find a hatchery shipping the exact species and size, and take its temperature, feed and acclimation guidance.
- Set the oxygen figure from the species’ source and check aeration and the outage plan against it, then size feed to planted area with the feed-balance chapter.
Reading: Aquaponics (HLA-6721) ↗ · Tilapia: Life History and Biology (SRAC 283) ↗ · Principles of Small-Scale Aquaponics (SRAC 5007) ↗ · Fish Health Management Considerations in Recirculating Aquaculture Systems—Part 3 ↗
06 / What changes on the plant side
NMSU CR680 states that vegetables grow best at 70–75°F and biofilter bacteria perform optimally at 77–86°F; SRAC 454 gives about 75°F as the best water temperature for most hydroponic crops, going as low as the mid-60s for most garden crops. SRAC 5007 says to match fish and plants with similar pH and temperature requirements. Tilapia and catfish bands overlap those figures; the trout band sits below all of them.
A trout system therefore expects slower nitrification and needs crops that accept a cool root zone, verified crop by crop; a decoupled plant loop that warms plant water separately is the structural answer, covered in the system-design comparison. Warm tilapia and catfish root zones hold less oxygen, so raft beds need their own aeration. Either way nutrient supply follows appetite: when SRAC 283’s 63°F cutoff arrives in an unheated tilapia tank, nutrient flow to the plants stops too, so plan lean winter plantings or heat the water for the plants as well.
Reading: Important Water Quality Parameters in Aquaponics Systems (CR680) ↗ · Aquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗ · Principles of Small-Scale Aquaponics (SRAC 5007) ↗ · Tilapia: Life History and Biology (SRAC 283) ↗
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 ExtensionAquaponics (HLA-6721) ↗
Coupled fish, microbes and plant needs.
- New Mexico State University ExtensionImportant Water Quality Parameters in Aquaponics Systems (CR680) ↗
Fish-system water chemistry, oxygen, temperature and nitrification.
- Southern Regional Aquaculture CenterTilapia: Life History and Biology (SRAC 283) ↗
Tilapia lower lethal temperature of 50–52°F for most species with blue tilapia tolerating about 48°F, feeding stopping below 63°F, survival of routine dawn dissolved oxygen below 0.3 mg/L, and the regulations note that many states restrict transport and culture of tilapia as non-indigenous species.
- Southern Regional Aquaculture CenterChannel Catfish: Life History and Biology (SRAC 180) ↗
Optimum channel catfish growth at about 85°F, metabolic rate doubling or halving per 18°F change, reduced growth below 4 ppm dissolved oxygen and a lethal level of about 1 ppm.
- Southern Regional Aquaculture CenterTrout Production: Feeds and Feeding Methods (SRAC 223) ↗
Optimum trout growing temperature of 55–65°F with feeding rates at their maximum there, the statement that above 68°F a trout’s digestive system does not use nutrients well, and the instruction to restrict feeding below 40°F or above 68°F.
- Southern Regional Aquaculture CenterTank Culture of Tilapia (SRAC 282) ↗
The statement that tank culture can have higher labor and energy costs for pumping and heating water than pond methods, the statement that warming large volumes of incoming water is generally not economically feasible without geothermal or waste heat, and the need for vigorous aeration in warm tilapia water together with its effect on solids; the recommended operating dissolved-oxygen range of 5.0–7.5 mg/L; and the statement that tank systems relying on continuous pumping, aeration or oxygenation risk major mortality without backup (alarms, oxygen storage, generators, quick response).
- Southern Regional Aquaculture CenterTrout Farming: Carrying Capacity and Inventory Management (SRAC 222) ↗
Dissolved oxygen and un-ionized ammonia as the primary limiting factors in Southern raceway trout culture, oxygen normally the more critical, and decreasing tank loadings when outflow dissolved oxygen drops below 6 ppm.
- Southern Regional Aquaculture Center · hosted by OSU ExtensionPrinciples of Small-Scale Aquaponics (SRAC 5007) ↗
Design, media-bed depth, biofilter sizing and aeration, potassium/calcium/iron supplementation and the UVI feed-to-area rule restated in ounces per square foot; applicability depends on system.
- University of Florida IFAS ExtensionFish Health Management Considerations in Recirculating Aquaculture Systems—Part 3 ↗
Biosecurity, quarantine, health monitoring and diagnosis.
- 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.
Choose viable fish: temperature, feed and purpose
Compare six practical fish groups, then narrow them by your actual water conditions and a verified hatchery plan.
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 & resilienceFish health, quarantine and daily operation
Prevent avoidable introductions, observe fish before symptoms escalate and keep records useful for diagnosis.
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 →