Size your aquaponics system from the ground up — fish tank volume, grow bed area, stocking density, pump GPH, daily feed, plant count, and annual harvest estimates. Covers media bed, NFT, DWC, and hybrid systems with tilapia, trout, catfish, bass, perch, bluegill, and koi.
Every aquaponics system is a miniature nitrogen cycle. Fish produce ammonia through their waste and respiration. Beneficial bacteria — primarily Nitrosomonas and Nitrobacter — colonize the grow media and convert that ammonia first into nitrite, then into nitrate. Plants absorb the nitrate as fertilizer, cleaning the water that flows back to the fish. Get the ratio right and the system is self-balancing. Get it wrong and either your fish die from ammonia toxicity or your plants starve for nutrients.
The standard beginner rule of thumb is a 1:1 ratio of fish tank volume to grow bed volume. A 100-gallon fish tank gets paired with a 100-gallon grow bed (typically a 4×8-foot bed filled 12 inches deep with expanded clay pebbles, which equals roughly 32 cubic feet or about 240 gallons — so in practice you often need slightly less media bed than the tank volume if the bed is deep). This ratio works because the grow media provides enough bacterial surface area and plant root mass to process the waste load from a moderately stocked tank.
For fish count, the practical rule is roughly 1 fish per 5–10 gallons of tank water for moderate-sized edible species like tilapia. A 200-gallon tank at moderate stocking density (1 lb/gallon) can support about 200 lbs of fish biomass. If your target harvest size is 1 lb per fish, that's 200 fish — but no one runs a 200-gallon tank at 200 fish all at once. In practice you stock at a fraction of max capacity, let fish grow, and harvest in batches. This calculator uses adult harvest weight to size the system, so results represent your maximum fully-stocked scenario at your chosen density.
NFT and DWC systems have different plant support ratios than media bed systems. NFT channels support fewer plants per unit of fish tank volume because there is less bacterial surface area (the biofilter must be added separately). DWC (raft) systems can support more plants per tank volume because the large raft area provides excellent root and bacterial surface. This calculator adjusts plant count estimates based on your chosen system type.
Aquaponics is a balancing act between three living systems — fish, bacteria, and plants — each with slightly different preferences. The following ranges represent the zone where all three can thrive simultaneously.
| Parameter | Ideal Range | Why It Matters |
|---|---|---|
| pH | 6.8 – 7.2 | Compromise zone where fish survive, bacteria thrive, and plants can uptake nutrients. Below 6.0 kills nitrifying bacteria. Above 7.5 locks out iron and manganese. |
| Ammonia (NH₃/NH₄⁺) | < 0.5 mg/L | Toxic to fish above 1–2 mg/L. Produced constantly by fish waste. A spike means your biofilter is not keeping up — reduce feed or add aeration. |
| Nitrite (NO₂⁻) | < 1 mg/L | Intermediate compound in nitrification. Toxic to fish above 5 mg/L ("brown blood disease"). Usually only a problem during system cycling or when the biofilter is stressed. |
| Nitrate (NO₃⁻) | 5 – 150 mg/L | Primary plant fertilizer in aquaponics. Fish tolerate up to 300+ mg/L; above 150 mg/L causes reduced plant growth. Very low nitrate (<5) means the system is understocked or plants are outpacing fish. |
| Dissolved Oxygen | > 6 mg/L | Fish and nitrifying bacteria are both aerobic. Below 4 mg/L fish become stressed; below 3 mg/L bacteria die off and ammonia spikes. Aerate aggressively at high stocking densities. |
| Water Temp (tilapia) | 70 – 85°F | Tilapia stop eating below 60°F and die below 50°F. They are the most forgiving species for warm climates but require heating in cold seasons. |
| Water Temp (trout) | 50 – 65°F | Trout require cold, well-oxygenated water. Above 70°F oxygen solubility drops and trout become heat-stressed. Ideal for cool-climate or basement systems with chiller units. |
| Iron (Fe) | 2 – 5 mg/L | Plants frequently show iron deficiency (yellowing between veins) in aquaponics. Supplement with chelated iron (EDTA or DTPA) when deficiency appears — fish-safe at typical doses. |
Tilapia are the gold-standard aquaponics fish for beginners and commercial operations alike. They tolerate crowding, fluctuating water quality, and a wide range of feeds. They grow from fingerling to harvest weight (around 1–1.5 lbs) in 6–9 months under good conditions. Their downside is temperature: they need water above 60°F and ideally 70–85°F to grow efficiently, which means heating costs in cold climates. Trout are the best cold-weather alternative — they grow quickly in 50–65°F water, taste excellent, and are well-suited to basement or mountain systems. Their weakness is a lower tolerance for poor water quality; dissolved oxygen must stay high, and ammonia spikes kill them faster than tilapia.
Catfish are a strong choice for hot climates. They tolerate low dissolved oxygen better than any other common aquaponics species, which gives you a buffer when the system heats up in summer. Bass and perch grow slower but have premium market value if you're selling. Bluegill are ideal for small hobby systems — they reproduce quickly, don't get too large, and will eat almost anything. Goldfish and koi are the best choice if you want to avoid eating your fish: they produce plenty of waste for plants, live for decades, and are nearly impossible to kill, making them the lowest-maintenance option for a plant-focused system.
The standard ratio for media bed systems is roughly 1 plant per gallon of fish tank water at moderate stocking. A 100-gallon tank supports about 100 plants — typically in a 4×4 bed if you're growing lettuce or herbs at 6-inch spacing. This breaks down for large, heavy-feeding plants like tomatoes, squash, or corn: a single tomato plant has the nutrient demand of 5–10 lettuce plants. Heavy feeders are best planted at a ratio of 1 per 5–10 gallons of fish tank volume and ideally in DWC or hybrid systems where nutrient delivery is more consistent. Leafy greens — lettuce, chard, basil, kale, spinach, watercress, pak choi — are the ideal aquaponics crops because their nutrient demand matches what a well-stocked tank produces at moderate density.
That depends entirely on your goals and climate. Aquaponics is genuinely impressive at two things: producing leafy greens year-round in a controlled environment, and producing fish protein in a small footprint with very low water use (90–95% less water than soil farming for equivalent plant production). If you live somewhere with a short growing season, expensive store produce, or limited land for soil gardening, an indoor or greenhouse aquaponics system can be a strong return on investment over 3–5 years. The startup cost is the honest downside: tanks, grow beds, pumps, aeration, plumbing, lighting for indoor systems, and heating for cold climates add up fast. A well-designed 200-gallon system with a proper grow bed will cost $1,000–$3,000 to set up from scratch using commercial components, or less with salvaged IBC totes and DIY construction. The operating costs are primarily electricity for the pump and heater, and fish feed. Most homesteaders find the system pays for itself in fish and greens over 2–4 years if they value their produce at retail prices.
Almost any vegetable will grow in aquaponics, but not all thrive equally. The best performers are fast-growing leafy greens with modest nutrient demands: lettuce (every variety), basil, mint, watercress, spinach, kale, chard, pak choi, arugula, and cilantro. These grow 2–3 times faster in aquaponics than in soil and require zero fertilization. Herbs like parsley, chives, and dill do extremely well. Fruiting vegetables — tomatoes, peppers, cucumbers, squash, and strawberries — can be grown but require a heavier stocking density or supplemental nutrients (iron and potassium especially) for maximum yield. Root vegetables like carrots, beets, and potatoes grow poorly in media beds because the growing medium interferes with root development — though some growers have success with beets in deep media beds. Avoid plants that require dry conditions between waterings (most succulent herbs and Mediterranean plants like rosemary and lavender struggle in the constantly moist growing environment of a recirculating system).