Cutting and Plumbing the IBC Tote
A week-by-week account of turning a used one-thousand-litre tote into a working fish tank, including the plumbing mistakes worth avoiding.
Documented garage to harvest crate
Can a 1,000-litre IBC tank feed a neighbourhood in Szczecin?
This blog tracks one closed-loop aquaponic system, month by month, through Polish winters and summers. Fish species, growth rates, electricity draw, feed costs and where the harvest actually gets sold, all logged in PLN. No starter kits, no live fish, nothing offered for sale here. Just the documentation.
The closed loop
A closed loop, tested indoors through a Polish winter
Aquaponics couples two familiar practices into one system. Fish live in a tank. Their waste, mostly ammonia, is converted by colonies of nitrifying bacteria into nitrates. Those nitrates become the primary nutrient feed for vegetables grown without soil, usually in gravel beds or floating rafts.
Water moves in one direction through the loop and returns filtered to the fish tank. No fertilizer added, no soil to manage, and the fish water gets scrubbed clean by the roots doing the work a filter would otherwise need to do.
It sounds simple on paper.
In practice, a Polish garage in January behaves nothing like a demonstration tank in a warm greenhouse. Insulation, pump sizing, heating cycles and bacterial colony stability all interact, and most of what gets published on this site started as a mistake worth writing down.
Why read this blog
What the documentation actually gives you
Every cost recorded in PLN
Electricity readings, feed bags, seedling trays and replacement parts are logged monthly, with receipts kept, so figures reflect an actual system rather than a rough estimate.
No kits, no fish for sale
Nothing here is a storefront. The site exists to publish findings from one household project, not to sell equipment, livestock or consulting services.
Failures published too
Pump failures, a lost batch of pak choi to root rot, an underestimated heating bill in February. The setbacks get written up alongside the parts that worked.
Local sales channels mapped
Notes on which markets, co-ops and neighbours actually took surplus greens and fish, and what that meant for a small household in Szczecin.
Species notes
Which fish tolerate a Polish garage all year
Indoor temperatures in an uninsulated garage swing hard between January and July. That range rules out a lot of species people associate with home aquaponics, and rewards a short list of hardier ones.
- African catfish (sum afrykański). Tolerates low oxygen and a wide temperature band. Growth slows noticeably below roughly 18°C, but it survives that stretch rather than dying off.
- Nile tilapia. Needs a stable 24 to 27°C. Reliable growth, but only with a heater running most of the year, which shows up directly on the electricity line of the monthly cost log.
- Crucian carp (karaś). Comfortable in cold, unheated cellar temperatures. Slower growth, but a reasonable backup species for the coldest months when heating gets scaled back.
- Goldfish, used only for cycling. Hardy enough to establish the bacterial colony before food fish go in. Ornamental only, never intended for consumption in this project.
Fastest to harvest
Which leafy greens reach harvest size fastest
Growth speed in an aquaponic raft or media bed depends on nutrient concentration, light hours and water temperature, and varies between batches. The figures below come from repeated sowings in the same system, not a single trial.
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Butterhead lettuce
Around 30 to 35 days from transplant to harvest size in this system, fairly forgiving of nutrient swings.
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Pak choi
Roughly 25 to 28 days. Responds quickly to higher nitrate levels, one of the more predictable crops logged so far.
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Arugula (rukola)
About 21 to 24 days for baby leaf size. Peppery flavour intensifies with cooler water temperatures.
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Watercress
Often the fastest, 18 to 21 days, but it needs continuous flow and struggles if the pump cycle stalls.
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Mizuna
Close to pak choi, around 24 days, with a milder mustard note and good tolerance for lower light.
Starter build
Building a starter system from one IBC tote
The tank at the centre of this whole project began as a single food-grade one-thousand-litre IBC tote, the kind used to ship liquids on pallets. Four stages turned it into a working system.
- Cutting and prepping the tank. The top third gets removed for a grow bed, the cage and pallet reused as a stand and frame.
- Plumbing and pump sizing. A submersible pump rated to the tank volume, bell siphon or timed flood-and-drain plumbing for the grow bed.
- Media and cycling. Expanded clay or lava rock media seeded with beneficial bacteria, run without fish for two to four weeks first.
- Stocking and monitoring. Fish introduced gradually, ammonia and nitrite tracked daily until the system stabilises.
Full parts lists, photos and the plumbing diagram used for this specific build are on the Installation Gallery page.
Running costs
What it actually costs to run, month to month
Costs shift with the season, mainly because of heating and grow-light hours, but the logged categories stay consistent.
CategoryTypical monthly range
Electricity (pump, heater, grow lights)120 to 260 zł
Fish feed60 to 110 zł
Water treatment and dechlorinator15 to 30 zł
Seedlings, rockwool, replacement media30 to 70 zł
Testing kits and consumables10 to 25 zł
Figures come from logged utility bills and receipts across one household system in Szczecin. They are not projections for any other setup and will vary with tank size, insulation and local electricity tariffs.
Selling the harvest
Where the harvest actually goes
A garage system this size rarely produces enough to justify a market stall on its own, but several smaller routes have worked, each documented as it was tried.
Weekend farmers markets in Szczecin accept small-batch greens from registered home producers on a case-by-case basis. A short-run neighbour subscription, a standing box of greens dropped off weekly, covered feed costs during the trial months without needing a formal storefront. A couple of small grocery co-ops expressed interest in hyper-local greens but wanted consistent weekly volume the system could not yet guarantee.
Selling food commercially in Poland, even at small scale, involves registration considerations such as rolniczy handel detaliczny for direct farm sales. This blog does not offer legal or tax advice; it only reports what routes were explored and what came of them.
From the build log
Recent notes from the tank
Six Months of Electricity Bills
Heating a fish tank through a Polish winter changes the electricity bill more than most other single factor in the system.
Selling the First Harvest
Notes from a first attempt at a Szczecin farmers market: what sold, what did not, and what the stall fee actually cost.
This is a documentation project, not a shop
Nothing on this site is offered for sale. No starter kits, no live fish, no paid consulting. The goal is a public, honest record of one closed-loop system, its costs in PLN, and whether small-scale aquaponics holds up as a plausible urban micro-business under Polish conditions. Questions about the method are welcome through the contact page.
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