# Aquaponics System Design: Fish Tank, Grow Bed, and Water Flow ## Key Takeaways - **Fish tank volume is the primary design driver**, dictating fish biomass capacity and subsequent nutrient production; target stocking densities of 0.25-0.5 lbs/gallon are recommended for stable nutrient cycling. - **Grow bed volume ratios are critical for nutrient processing balance**, with media beds requiring a 1:1 to 2:1 ratio to fish tank volume, while raft systems can operate with leaner ratios (0.5:1 to 1:1). - **Water flow rates must be sufficient to support biological filtration and oxygenation**, targeting 1-2 system volumes per hour for media beds and 4-6 system volumes per hour for raft systems. - **Grow bed media depth should be matched to crop requirements**, with leafy greens needing 8-12 inches and fruiting crops requiring 12-16 inches to support root development and nutrient uptake. - **System redundancy and emergency preparedness are paramount**, necessitating design considerations for emergency drainage and backup pumps to mitigate fish mortality risks from power outages. - **Rigorous water quality monitoring is essential**, with daily testing for the first month and weekly thereafter for ammonia, nitrite, nitrate, pH, and dissolved oxygen to maintain optimal conditions for fish and plant health. --- Aquaponics combines [fish farming](/knowledge/animal-farming/aquaculture/fish-farming-water-feed-stocking-biosecurity-welfare-and-harvest-decisions) with soil-less plant production in a single recirculating system. The fish provide nutrients for the plants, and the plants clean the water for the fish. This guide covers the core decisions you need to make when planning a new system: fish tank sizing, grow bed configuration, and water flow rates. It is written for farmers, homesteaders, and agricultural planners who want to build a working system on a small commercial or large backyard scale. You will find practical numbers, step by step guidance, and clear thresholds for when to adjust your design before you pour concrete or cut pipe. ## At a Glance - **Fish tank size drives everything else.** Start with the fish species and target harvest weight, then size the tank to hold the fish at their final density. - **Use a 1:1 to 2:1 grow bed to fish tank volume ratio** for media beds. Raft systems can run leaner on grow bed volume. - **Flow rate target is 1 to 2 times the total system volume per hour** for most media bed systems. Raft systems can push 4 to 6 times per hour. - **Keep [fish stocking density](/knowledge/animal-farming/aquaculture/fish-stocking-density-how-to-make-a-responsible-decision) between 0.25 and 0.5 pounds of fish per gallon** of fish tank water for steady nutrient production. - **Match your grow bed media depth to your crop.** Leafy greens need 8 to 12 inches, fruiting crops need 12 to 16 inches. - **Design for emergency drainage and a backup pump.** A power outage kills fish faster than any other single failure. - **Test water daily for the first month**, then weekly once the system cycles and stabilizes. ## Understanding the Aquaponics System Design Basics Aquaponics system design starts with understanding the three living components and how they interact. The fish produce ammonia through their gills and waste. Bacteria in the grow bed convert that ammonia to nitrite and then to nitrate, which plants take up as food. The plants also absorb other nutrients from the fish waste, and the roots physically filter particulates from the water. The water then returns to the fish tank clean enough for the fish to thrive. The design challenge is balancing these three components so that no single part overwhelms the others. Too many fish and the water becomes toxic. Too few fish and the plants starve. Too much grow bed volume and the bacteria convert nutrients faster than the plants can use them. Too little grow bed volume and the water leaves the system with excess nutrients that can harm the fish. The most common mistake new builders make is choosing a fish tank because it looks nice or is on sale, then trying to fit everything else around it. That approach works against you. The correct sequence is to decide what you want to eat or sell, calculate the fish load that supports that goal, then size the grow bed and pump to match the fish. ## Choosing Your Fish Species First Your fish species determines your water temperature, your stocking density, and your harvest schedule. Warm water fish like tilapia and catfish grow fast and tolerate lower water quality. Cold water fish like trout and salmon require higher oxygen levels and cooler temperatures. In between are species like yellow perch, bass, and hybrid striped bass that grow in moderate temperatures. Tilapia is the most common choice for new aquaponics operators for good reasons. It grows quickly, tolerates a wide temperature range from 72 to 86 degrees Fahrenheit, and accepts a variety of feeds. It also withstands lower oxygen levels and higher ammonia levels than most other species. If you are building your first system and you live in a region where tilapia is legal to raise, start with tilapia. Catfish is another practical choice for warmer climates. It grows well at temperatures from 75 to 85 degrees Fahrenheit and is very hardy. Channel catfish are the standard commercial species. They grow slower than tilapia in the first few months but reach a solid harvest weight at 12 to 18 months. Trout requires the most careful water quality management. Rainbow trout need water temperatures below 70 degrees Fahrenheit, ideally between 55 and 65 degrees. They also need dissolved oxygen levels above 6 parts per million at all times. If you have a cold water source or live in a cool climate, trout can work, but you need a larger grow bed per pound of fish because trout produce more ammonia per pound of feed than warm water species. Koi and goldfish are common in small backyard systems and are useful for cycling a new system before you add food fish. They are hardy and forgiving of water quality swings. Many new operators use them to establish the bacterial colony, then move them out and add their food fish. Your climate and your water source matter as much as your preference. If you have a cold winter and no greenhouse, tilapia will not survive without a heater. If you have a hot summer and no shade, trout will not survive without a chiller. Match your species to your environment, not the other way around. ## Aquaponics Fish Tank Size: The Starting Point The fish tank is the engine of your system. It holds the fish, receives the returning water from the grow bed, and provides the volume that buffers water quality swings. The size of your fish tank determines how many fish you can raise and therefore how many nutrients you produce for your plants. ### Calculating Fish Tank Volume Start with your production goal. Decide how many pounds of fish you want to harvest per cycle. A reasonable starting goal for a small commercial system is 100 pounds of fish per cycle. A backyard system might target 20 to 40 pounds. The formula is simple: **Fish tank volume in gallons = Target fish weight in pounds / Target stocking density in pounds per gallon** For a stocking density of 0.33 pounds per gallon, which is a comfortable middle ground: - 20 pounds of fish needs about 60 gallons - 40 pounds of fish needs about 120 gallons - 100 pounds of fish needs about 300 gallons - 500 pounds of fish needs about 1,500 gallons These numbers assume you are raising fish to a harvest weight of 1 to 1.5 pounds each. If you raise larger fish, you need more volume per fish because larger fish produce more waste per pound of body weight. ### Matching Tank Size to Fish Count Once you know your total volume, calculate how many fish you can hold. Divide your target harvest weight by the average weight per fish at harvest. For example, if you want 100 pounds of tilapia and you harvest at 1.25 pounds per fish, you need 80 fish. If you harvest at 2 pounds per fish, you need 50 fish. The tank volume stays the same because the total biomass is the same, but the number of individual fish changes. The tank depth matters for fish health. Most fish species do best in tanks that are at least 24 inches deep. Deeper tanks provide more vertical space and help maintain stable temperatures. Shallow tanks heat up and cool down quickly and stress the fish. ### Tank Shape and Material Round tanks are the best shape for fish health. They promote circular water flow, which keeps waste moving toward the center drain. They also eliminate corners where fish can become trapped or where dead zones can form. If you cannot use a round tank, use an oval or a square tank with rounded corners. Common tank materials include: - **Fiberglass** is durable, non-toxic, and easy to clean. It is the most common commercial choice but is more expensive. - **Polyethylene plastic** is affordable and widely available. Food grade tanks are safe for fish. Look for tanks rated for potable water. - **Concrete** is permanent and heavy. It requires a waterproof sealant and must be cured properly before adding fish. - **Metal stock tanks** are inexpensive but can corrode. Use a food grade liner if you choose this option. Avoid tanks made from copper, galvanized steel, or any material that can leach metals into the water. Fish are sensitive to copper and zinc at very low concentrations. ## Grow Bed Design: Where the Plants Live The grow bed is where your plants grow and where your beneficial bacteria live. It serves two functions in the system. It provides physical support for plant roots and a surface for nitrifying bacteria to colonize. The grow bed also acts as a mechanical filter, trapping solid waste from the fish tank. ### Grow Bed Volume Ratio The ratio of grow bed volume to fish tank volume is one of the most important design decisions you will make. It determines how much nutrient processing capacity your system has. For media bed systems, which use gravel or clay pebbles as the growing medium, use a ratio of 1:1 to 2:1 grow bed volume to fish tank volume. This means a 300 gallon fish tank needs 300 to 600 gallons of grow bed volume. The higher ratio gives you more buffer capacity and allows you to grow a wider variety of plants. The lower ratio is more efficient with space and water but requires more careful monitoring. For raft systems, where plants float on styrofoam rafts over a deep channel of water, use a ratio of 0.5:1 to 1:1. Raft systems can run leaner because the water column itself provides some biological filtration. The plant roots hang directly into the water and absorb nutrients continuously. For nutrient film technique systems, where a thin film of water flows through channels, use a ratio of 0.25:1 to 0.5:1. NFT systems rely heavily on a separate biofilter because the channels provide very little surface area for bacteria. ### Media Depth and Type The depth of your grow bed media determines what you can grow. Shallow beds of 6 to 8 inches support leafy greens and herbs. Medium beds of 10 to 12 inches support most vegetables. Deep beds of 14 to 16 inches support fruiting crops like tomatoes, peppers, and cucumbers. The media itself needs to provide surface area for bacteria, allow water to flow freely, and support plant roots. The most common options are: - **Expanded clay pebbles** are lightweight, pH neutral, and excellent for bacteria colonization. They are the most popular choice but can be expensive in bulk. - **Gravel** is cheap and heavy. Use pea gravel or river rock that is 3/8 to 3/4 inch in diameter. Avoid limestone gravel because it raises pH. - **Lava rock** is lightweight, porous, and provides excellent surface area. It can be sharp and difficult to work with. - **Perlite and vermiculite** are lightweight but float. They are best used in combination with heavier media. Fill the grow bed to the depth you need for your crop. Do not fill it to the top of the container. You need several inches of freeboard above the media to allow for flood and drain cycles. ### Grow Bed Configuration Media beds can be built as flood and drain beds, where the water rises to fill the bed and then drains away, or as constant flow beds, where water continuously flows through the media. Flood and drain beds are the most common for small and medium systems. The cycle of filling and draining pulls oxygen into the root zone, which is essential for healthy root development. The drain cycle also flushes waste through the media and prevents anaerobic zones from forming. The flood and drain cycle should run 4 to 8 times per hour. Each cycle takes 10 to 15 minutes. You control the cycle with a bell siphon or a timer-controlled pump. Bell siphons are mechanical and require no electricity, but they can be finicky to tune. Timer controlled pumps are simpler but require a pump that can handle frequent starting and stopping. ## Aquaponics Water Flow: Sizing the Pump and Plumbing Water flow is the circulatory system of your aquaponics setup. It moves oxygen to the fish, nutrients to the plants, and waste to the bacteria. Getting the flow rate right is critical for both fish health and plant growth. ### Understanding Flow Rate Flow rate is measured in gallons per hour. The target flow rate depends on your system type and your grow bed volume. For media bed systems, aim for a flow rate that moves 1 to 2 times the total system volume per hour. If you have a 300 gallon fish tank and 400 gallons of grow bed volume, your total system volume is about 700 gallons. Your pump should move 700 to 1,400 gallons per hour. For raft systems, aim for 4 to 6 times the total system volume per hour. The faster flow keeps the water well oxygenated and prevents solids from settling in the channels. For NFT systems, aim for 1 to 2 gallons per minute per channel. The channels are shallow, so the water moves quickly through them. ### Calculating Pump Size Pump size is rated by flow rate at a given head height. Head height is the vertical distance the pump must push water. A pump rated at 800 gallons per hour at zero head will deliver much less at a head of 4 or 5 feet. To size your pump: 1. Measure the vertical distance from the water surface in the fish tank to the highest point of your grow bed inlet. This is your static head. 2. Add 1 foot of head for every 10 feet of horizontal pipe run. This accounts for friction loss. 3. Add 1 to 2 feet of head for elbows, valves, and other fittings. 4. Total these numbers to get your dynamic head. 5. Look at pump curves and select a pump that delivers your target flow rate at your dynamic head. A common mistake is buying a pump based on the flow rate at zero head. The pump ends up delivering half the needed flow once it is installed. Always check the pump curve. ### Plumbing Layout Your plumbing layout needs to move water from the fish tank to the grow bed and back again. The return path from the grow bed back to the fish tank should use gravity. Position the grow bed above the fish tank so the water can drain back down. The pump sits in the fish tank or in a sump tank below the fish tank. It pushes water up to the grow bed. The grow bed fills and then drains back to the fish tank through a drain line. Key plumbing components: - **A ball valve** on the pump outlet lets you adjust flow rate. - **A check valve** prevents water from flowing backward through the pump when it is off. - **A standpipe** in the fish tank sets the water level and prevents overflow. - **Aeration stones** in the fish tank supplement dissolved oxygen. - **A solids filter** or settling tank between the fish tank and grow bed removes solid waste before it reaches the plants. ### Solids Management Fish produce solid waste in addition to dissolved ammonia. If this solid waste accumulates in the grow bed, it can clog the media and create anaerobic zones. Anaerobic bacteria produce hydrogen sulfide, which is toxic to both fish and plants. For small systems, a simple settling tank or swirl separator before the grow bed removes most solids. The solids settle to the bottom and you drain them out weekly. For larger systems, a mechanical filter such as a drum filter or bead filter is worth the investment. These filters remove solids continuously and require minimal labor. Solids removal is not just about preventing clogs. The solids contain phosphorus and other nutrients that plants need. If you remove too many solids, your plants may develop nutrient deficiencies. The goal is to remove the bulk of the solids but leave some particulate matter in the water for the plants. ## Step by Step System Design Process Follow this sequence to design a complete aquaponics system from scratch. This process assumes you are building a media bed system, which is the best choice for most new operators. ### Step 1: Define Your Production Goals Write down what you want to produce. Include the fish species, the target harvest weight, the number of fish per cycle, and the types of plants you want to grow. Be specific. A goal of "some fish and vegetables" is not enough to design around. A realistic starting goal for a small commercial system is 500 pounds of tilapia per year and 2,000 heads of lettuce per year. A backyard system might target 50 pounds of fish per year and 200 heads of lettuce. ### Step 2: Calculate Fish Tank Volume Using the formula from the fish tank section, calculate your tank volume. Write this number down. It is the anchor for all your other calculations. ### Step 3: Select Your Grow Bed Ratio Decide on your grow bed to fish tank ratio. For a first system, use 1.5:1. This gives you a comfortable buffer without requiring excessive space. Multiply your fish tank volume by 1.5 to get your grow bed volume. ### Step 4: Design the Grow Bed Layout Decide how many grow beds you need and their dimensions. A standard grow bed is 4 feet wide and 8 feet long, which gives a surface area of 32 square feet. At a media depth of 12 inches, that bed holds 32 cubic feet of media, which is about 240 gallons. Divide your total grow bed volume by the volume per bed to get the number of beds you need. ### Step 5: Calculate Media Volume Multiply your total grow bed volume by 0.75 to account for the space taken up by the media. A 240 gallon grow bed needs about 180 gallons of media. In cubic feet, that is about 24 cubic feet. ### Step 6: Size the Pump Calculate your total system volume by adding the fish tank volume and the grow bed volume. Multiply by 1.5 to get your target flow rate in gallons per hour. Then calculate your dynamic head and select a pump. ### Step 7: Plan the Plumbing Draw a diagram of your system showing the fish tank, grow bed, pump, and all plumbing lines. Mark the pump location, the grow bed inlet, the drain line, and the return line. Include valves and check valves in your diagram. ### Step 8: Build a Budget List every component you need and estimate the cost. Include the tank, grow bed containers, media, pump, plumbing, aeration, and testing supplies. Add 15 percent for items you forgot or that need adjustment. ## Common Design Mistakes and How to Avoid Them ### Mistake 1: Oversizing the Fish Tank for the Grow Bed A large fish tank with a small grow bed is the most common design error. The fish produce more ammonia than the bacteria and plants can process. The water becomes toxic and the fish die. The fix is to follow the 1:1 to 2:1 ratio. If you already have a large tank, expand your grow bed capacity before you add fish. ### Mistake 2: Undersizing the Pump An undersized pump delivers too little flow. The water in the fish tank becomes stagnant and low in oxygen. The grow bed does not cycle properly and anaerobic zones form. The fix is to calculate your flow rate requirement before you buy a pump and check the pump curve at your dynamic head. ### Mistake 3: Using the Wrong Media Some media types are unsuitable for aquaponics. Limestone gravel raises pH and can make nutrients unavailable to plants. Sand compacts and prevents water flow. Expanded clay pebbles that are too small can clog the drain. The fix is to use media that is 3/8 to 3/4 inch in diameter and is pH neutral. Rinse the media thoroughly before installing it. ### Mistake 4: No Solids Removal If you skip solids removal, the grow bed gradually clogs with fish waste. Water flow slows and anaerobic zones form. The system becomes difficult to manage and plant growth suffers. The fix is to include a settling tank or mechanical filter in your design. This is not optional for a system that will run for more than a few months. ### Mistake 5: No Backup Power A power outage of even a few hours can kill your fish if the pump stops and the water becomes stagnant. This is the single most common cause of fish loss in aquaponics. The fix is to have a battery backup pump or a generator. A simple battery powered air pump that runs during outages can keep the fish alive for several hours. ### Mistake 6: Starting with Too Many Fish New operators often add too many fish at once. The bacterial colony in the grow bed takes 4 to 8 weeks to establish. If you add a full fish load immediately, the ammonia spikes and kills the fish. The fix is to cycle the system first. Add a small number of hardy fish or use pure ammonia to establish the bacteria. Test the water daily until ammonia and nitrite levels drop to zero, then add your fish gradually. ## Decision Thresholds for System Adjustments Knowing when to adjust your system is as important as the initial design. These thresholds help you recognize problems before they become crises. ### Ammonia Levels Ammonia is toxic to fish even at low levels. Test for total ammonia nitrogen weekly. - **Below 1 ppm:** Safe. Your bacteria are keeping up with the fish load. - **1 to 3 ppm:** Caution. Reduce feeding and check your bacterial colony. Add more grow bed media if possible. - **Above 3 ppm:** Danger. Stop feeding for 24 to 48 hours. Do a partial water change of 20 to 30 percent. Check your biofilter. ### Nitrite Levels Nitrite is the intermediate product of the nitrogen cycle. It is also toxic to fish. - **Below 1 ppm:** Safe. - **1 to 2 ppm:** Caution. Reduce feeding and add aeration. - **Above 2 ppm:** Danger. Stop feeding and do a partial water change. Add salt to protect the fish from nitrite toxicity. ### Nitrate Levels Nitrate is the final product of the nitrogen cycle and is much less toxic than ammonia or nitrite. Plants use it as fertilizer. - **Below 20 ppm:** Low. Your plants may be nutrient limited. Consider reducing plant density or adding more fish. - **20 to 80 ppm:** Optimal for most systems. - **Above 150 ppm:** High. Plants may still grow, but the water is becoming concentrated. Increase plant density or do a partial water change. ### Dissolved Oxygen Fish need dissolved oxygen above 5 ppm for most species. Trout and some other cold water fish need above 6 ppm. - **Above 6 ppm:** Optimal. - **4 to 6 ppm:** Acceptable for warm water fish but monitor closely. - **Below 4 ppm:** Danger. Increase aeration immediately. Check your pump flow rate. ### pH Levels Aquaponics systems naturally drift toward acidity as the bacteria produce nitric acid. The target pH range is 6.8 to 7.0. - **6.5 to 7.5:** Acceptable range. - **Below 6.5:** Bacteria activity slows and nutrient availability drops. Add potassium hydroxide or calcium hydroxide to raise pH. - **Above 7.5:** Nutrient availability drops, especially iron and phosphorus. Add small amounts of acid to lower pH. ### Water Temperature Temperature affects fish metabolism and the rate of the nitrogen cycle. - **Warm water fish (tilapia, catfish):** 75 to 85 degrees Fahrenheit. - **Cool water fish (yellow perch, bass):** 65 to 75 degrees Fahrenheit. - **Cold water fish (trout):** 55 to 65 degrees Fahrenheit. If your water temperature is outside these ranges for more than a few days, you need a heater or chiller. ## Monitoring and Recordkeeping for Your Aquaponics System Consistent monitoring is the difference between a system that thrives and one that fails. You need a testing routine and a recordkeeping system to track trends over time. ### Daily Checks Check these items every day, ideally at the same time each morning: - **Water flow:** Confirm the pump is running and water is flowing through the grow bed. - **Fish behavior:** Watch for fish at the surface, gasping, or swimming erratically. - **Feed response:** Fish should come to the surface when you feed them. - **Water temperature:** Check the thermometer and log the reading. - **System leaks:** Look for wet spots around the tank, grow bed, and plumbing. ### Weekly Tests Test these parameters weekly and log the results: - Ammonia - Nitrite - Nitrate - pH - Dissolved oxygen Use a test kit designed for aquaponics or aquaculture. Liquid test kits are more accurate than test strips. Calibrate any electronic meters monthly. ### Monthly Tasks - **Clean the settling tank or mechanical filter.** - **Inspect the grow bed media for clogging.** - **Check all plumbing connections for leaks.** - **Clean the pump intake and impeller.** - **Trim plant roots that are blocking drains.** ### Recordkeeping Keep a simple logbook or spreadsheet with columns for date, water temperature, ammonia, nitrite, nitrate, pH, dissolved oxygen, fish feeding rate, and any observations. Review the log weekly to spot trends before they become problems. A steady rise in ammonia over several days means your bacteria are not keeping up. A steady drop in pH means your system is becoming acidic. A drop in dissolved oxygen may mean your pump is failing or your aeration stones are clogged. ## When to Call a Veterinarian or Extension Agent Most aquaponics problems are system problems, not animal health problems. You can solve them with water testing and adjustments. But some situations require professional help. ### Call a Veterinarian When - **Fish are dying and you cannot identify the cause.** A veterinarian with aquaculture experience can perform a necropsy and identify bacterial, viral, or parasitic causes. - **Fish show visible lesions, ulcers, or abnormal growths.** These can be signs of bacterial infections that may require treatment. - **Fish are swimming abnormally or spinning.** This can indicate a neurological issue or a parasite infection. - **You need to treat fish with antibiotics or other medications.** Many medications require a veterinary prescription. ### Call an Extension Agent When - **You are planning a new system and want a design review.** Extension agents can help you avoid costly mistakes. - **Your water source has unusual chemistry.** High iron, high hardness, or contamination may require special treatment. - **Your plants show nutrient deficiencies that do not respond to standard fixes.** An extension agent can help you diagnose the issue. - **You want to scale up from a backyard system to a commercial operation.** Extension agents can help with business planning and regulatory compliance. ### Call a Regulatory Agency When - **You are raising fish species that are regulated in your state.** Some states restrict tilapia and other non-native species. - **You are selling fish or produce commercially.** You may need permits and inspections. - **You are using well water and need to test for contamination.** Your local health department can guide you. ## Scaling Up Your System Once you have a working system and you understand the daily rhythms, you may want to scale up. Scaling up is not just building a bigger version of the same system. The economics and the management change. ### Add Multiple Independent Systems Instead of building one very large system, build several medium systems that operate independently. This gives you redundancy. If one system has a water quality problem, you can isolate it without losing your entire crop. ### Consider a Sump Tank A sump tank is a separate tank that collects water from the grow beds and returns it to the fish tank. It provides a place to add make-up water, test water quality, and house the pump. It also allows you to run the grow beds and fish tank at different water levels. ### Automate Where It Matters Automation is worth the investment for feeding, water testing, and pH control. Automated feeders ensure consistent feeding even when you are away. Continuous water quality monitors can alert you to problems before they become crises. Automated pH controllers can drip base into the system to maintain the target range. ### Plan for Waste Management A commercial scale system produces significant solid waste. Plan for how you will dispose of the solids removed from the settling tank. Composted fish waste is an excellent soil amendment for field crops. You can also sell it as a value added product. ## Frequently Asked Questions ### How long does it take to cycle a new aquaponics system? Cycling a new system takes 4 to 8 weeks. The process involves establishing a colony of nitrifying bacteria in the grow bed. You can speed it up by adding a small amount of pure ammonia daily, keeping the water temperature at 75 to 80 degrees Fahrenheit, and maintaining a pH between 7.0 and 8.0. You can also add a handful of gravel or media from an established system to jump start the bacterial colony. ### Can I use tap water in my aquaponics system? Yes, but you must dechlorinate it first. Chlorine and chloramine are toxic to fish and bacteria. Let the water sit for 24 hours to allow chlorine to evaporate, or use a dechlorinating product. Chloramine does not evaporate, so you must use a chemical treatment. Test your tap water for heavy metals and other contaminants before you use it. ### How many fish can I put in a 100 gallon tank? At a stocking density of 0.33 pounds per gallon, a 100 gallon tank can support about 33 pounds of fish at harvest. If you harvest tilapia at 1.25 pounds each, that is about 26 fish. Start with fewer fish, about 15 to 20, to allow the system to establish before you add the full load. ### What is the best grow bed media for a beginner? Expanded clay pebbles are the best choice for most beginners. They are lightweight, pH neutral, and provide excellent surface area for bacteria. They are also reusable and easy to clean. The main downside is cost. If you are on a tight budget, pea gravel is a good alternative. ### How often should I feed my fish? Feed your fish 2 to 3 times per day. Feed only what they will consume in 5 minutes. Overfeeding is a common cause of water quality problems. The feeding rate also determines the nutrient production for your plants. As a rule, you need about 1 pound of fish feed per day for every 100 square feet of grow bed surface area. ### Do I need a biofilter if I have a grow bed? No, the grow bed media serves as your biofilter. The bacteria colonize the surface of the media. In a media bed system, the grow bed is the biofilter. If you have a raft or NFT system, you need a separate biofilter because the plant channels do not provide enough surface area for bacteria. ### Can I grow fruiting crops like tomatoes in a media bed? Yes, but you need a deep media bed of at least 12 to 14 inches. Fruiting crops have larger root systems and need more support than leafy greens. They also need more nutrients, which means you need a higher fish stocking density. Plan for a grow bed to fish tank ratio of at least 1.5:1 if you want to grow fruiting crops. ### What happens to the plants during a power outage? Plants can survive several hours without water flow, but the fish cannot. The priority during a power outage is to keep the fish alive. Use a battery powered air pump to maintain oxygen in the fish tank. The plants will be fine for a few hours. If the outage lasts more than a day, you may need to manually water the plants with water from the fish tank. ## Related Farming Guides This section will be populated with links to related farming guides on aquaponics, fish farming, and soil-less agriculture. Check back for updates. ## Related Clinical & Scientific Guides * [Animal Welfare Audits: Building a Useful Farm Program](/knowledge/animal-farming/farm-management/animal-welfare-audits-building-a-useful-farm-program) * [Total Mixed Ration (TMR) for Dairy: Mixing and Feeding Management](/knowledge/animal-farming/farm-management/total-mixed-ration-dairy-mixing-feeding) * [Feed Additives for Livestock: Probiotics, Enzymes, and More](/knowledge/animal-farming/farm-management/feed-additives-livestock-probiotics-enzymes) - [Aquaponics vs Hydroponics: Differences, Costs and Which to Choose](/knowledge/veterinary-medicine/aquarium-fish-care/aquaponics-vs-hydroponics) ## References - USDA Farm Management: https://www.farmers.gov/ - FAO Farm Management: https://www.fao.org/farmer-field-schools/en/ - FAO Animal Production and Health: https://www.fao.org/animal-production/en/ - WOAH (World Organisation for Animal Health): https://www.woah.org/en/home/ > This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.