Closed-System Kuruma Prawn Farming: Boost Yield & Slash Risk

Let’s talk about prawns. More specifically, let’s talk about growing them in a way that doesn’t keep you up at night worrying about disease wiping out your entire stock or sudden weather changes turning your pond into a disaster zone. That’s the promise of closed-system kuruma prawn farming. It sounds fancy, but strip away the jargon and it’s really about taking control. You’re building a mini-ocean in a tank, and you get to be the weather god, the water quality manager, and the head chef all at once. No more praying for good rains or fighting off pollutants from upstream. It’s just you and your prawns, in a controlled dance towards harvest. So, how do you actually do it? Let’s roll up our sleeves and get into the nitty-gritty, the stuff you can start planning for tomorrow.

The first brick in this closed-system fortress is the tank itself. Forget massive, sprawling ponds. We’re talking circular or rectangular tanks, typically made of durable fiberglass or coated concrete, with a conical bottom. That cone is not for looks; it’s your waste management system. All the gunk—uneaten feed, prawn poop—settles right into that center point, making it a breeze to flush out daily. Size? For a manageable start, think 10 to 20 cubic meters. It’s big enough to be worthwhile but small enough that you can monitor every square inch like a hawk. Place it under a simple greenhouse-style shelter. That roof isn’t just for shade; it’s your primary defense against acid rain, leaf litter, and unwanted critters diving in for a snack. You’ve just excluded 50% of your traditional farming headaches with a tank and a roof.

Now, the water. This is where the ‘closed’ part really kicks in. You start by filling your tank with filtered seawater or, if you’re inland, a synthetic salt mix. Then you treat it. And I mean really treat it. Chlorinate it to wipe out any lurking pathogens, then neutralize the chlorine with a hefty dose of sodium thiosulfate. Next, you inoculate it with beneficial bacteria—the kind you buy in a bottle from any aquaculture supplier. These little guys are your unseen workforce. They’ll break down ammonia and nitrites. You’ll cycle this water for a good two to three weeks before a single prawn post-larva goes in. This isn’t patience; it’s building an ecosystem. Once the prawns are in, you’re not doing massive water changes. You’re topping up for evaporation losses, maybe swapping out 5-10% weekly if your filters are keeping up. The goal is stability, not exchange.

Which brings us to the life support system: filtration and aeration. This isn’t optional; it’s the lungs and kidneys of your operation. Get a robust protein skimmer. It pulls out dissolved organic waste before it can break down and foul the water. Pair it with a simple but effective biological filter—a moving bed bioreactor (MBBR) is perfect. It’s just a chamber filled with tiny plastic chips that tumble around, giving your beneficial bacteria a massive surface area to live on. And then, aeration. Don’t be shy. You want diffuser stones or airlift pumps creating a literal boiling effect on the tank bottom. Kuruma prawns need oxygen, and their waste needs to be kept suspended so it can head to the central drain. A power failure? Have a backup generator wired to kick in automatically within minutes. Your prawns can survive many things, but not 30 minutes without oxygen.

Stocking is where greed can trip you up. In an open pond, you might stock 20-30 post-larvae per square meter and hope for the best. In your controlled tank, you can go denser, but smartly. Aim for 100-150 post-larvae per cubic meter of water. The key is using high-health, specific pathogen-free (SPF) seeds from a reputable hatchery. It costs more upfront, but it’s cheaper than a disease outbreak. Acclimate them slowly over an hour, dripping tank water into their transport bag. Don’t just dump them in; they’ve had a stressful trip.

Feeding is an art form here. You’re not feeding the prawns; you’re feeding the water system. Overfeeding is the fastest way to crash your water quality. Use high-quality, slow-sinking pellets. Start with frequent, tiny meals—maybe 5-8 times a day if you can automate it with a feeder. Watch your feeding trays. If feed is left after 90 minutes, you’re giving too much. Cut back immediately. As they grow, you’ll adjust the pellet size and frequency. Keep a feed chart on the wall and log everything. Their appetite is your best daily health report.

Daily routine? It’s simple but non-negotiable. First thing in the morning, check the oxygen levels and temperature. Then, flush out the central drain waste. Check your filters, backwash if needed. Observe the prawns. Are they swimming actively? Are their guts full? Is the shell looking good? Test the water. Not just for pH and salinity, but for the invisible killers: ammonia and nitrite. They should always be at zero. Nitrate will creep up; that’s your cue for a small, controlled water change. This daily hands-on time is where you catch problems when they’re still small whispers, not screams.

Harvesting is the fun part. Because your tank is controlled and your prawns are less stressed, you can do partial harvests. Use a seine net to scoop out the bigger ones, letting the smaller ones grow for another week or two. This means a steadier cash flow and a higher average size. When it’s all done, you don’t just drain the pond into the environment. You treat the wastewater through settlement and filtration before discharge. Being a closed system is a responsibility, not just a technique.

So, what’s the bottom line? Closed-system farming asks for more investment upfront in tanks, roofs, and filters. It demands relentless daily attention to detail. But in return, it gives you predictability. You’re not farming at the mercy of nature anymore. You’re running a production line where you control the variables. Your yields are consistently higher—you can realistically target 5-10 kilograms per cubic meter per crop. Your risks from disease and weather are slashed. It turns prawn farming from a gamble into a skilled craft. And that’s a feeling worth building a tank for.