Seedling Nursery - Thùng Ươm Cây Giống Thủy Canh (Kratky Method)

Seedling Nursery — Passive DWC Tub with 3 Locking Net-Pot Sockets

A 2 L indoor water-culture tub for rooting seedlings under a grow light before they go out to the tower.

The sockets are dimensional copies of the ones in Modular Hydroponic Tower by blove, so the same 2 inch net pots that lock into that tower lock into this one. Start seedlings indoors, pull them out when the roots are ready, and drop them straight into the tower with no repotting and no transplant shock.

Why it exists

Seedlings need a real root system before they'll hold their own in an outdoor tower. Rockwool plugs on a tray dry unevenly and the roots stay shallow. A few weeks in still, nutrient-rich water lets the roots chase a falling waterline downward, which is exactly what builds the long root mass you want at transplant.

How it works

No pump, no air stone, no power. Fill to 85 mm deep and the waterline sits right at the bottom of the net pots. As the seedlings drink, the level drops and opens an air gap — roots below stay wet, roots in the gap breathe. That's the Kratky method, and for seedlings it works better than bubbling air through a tub this small.

Three Ø5 mm vents pass through the wall above the waterline so the air gap can exchange with the room. They're in the wall rather than the lid on purpose: a grow light shining straight down through lid holes will give you an algae bloom inside a week. Print it in an opaque colour for the same reason.

Specs

• Reservoir — Ø180 × 143 mm, 2.5 mm wall, 3 mm floor

• Interior — Ø175 × 140 mm

• Working volume — 2.04 L at the 85 mm fill line, about 0.68 L per plant

• Lid — Ø180 × 4 mm with a 6 mm skirt that locates it inside the rim

• Sockets — 3, on a Ø92 bolt circle, 21 mm deep, 79.7 mm centre to centre

• Pot compatibility — 2 inch net pots, same as the parent tower

• Socket bore — Ø60.58 with a 45° lead-in chamfer from Ø64

• Locking lugs — three per socket, 30° of arc at 120°, 3.55 mm proud of the bore, 45° flanks, 1.5 mm crest, centred 6 mm below the face

• Assembled height — 147 mm

• Fits a 250 × 210 bed (Prusa MK3S) and anything larger

Print settings

Neither part needs supports.

• Reservoir — open side up, flat base on the bed

• Lid — top face down on the bed; every overhang is 45° or steeper

• Material — PETG. PLA creeps and softens in permanent standing water

• Layer height — 0.2 mm

• Perimeters — 6 or more. The wall is 2.5 mm and you want it filled entirely with perimeters, with no infill running through it

• Solid layers — 8 bottom, 6 top

• Infill — 20%, barely used

• Cooling — 30% or less. Low fan on PETG means better layer bonding, and layer bonding is what makes it hold water

• Roughly 490 g and somewhere around 25 hours for the pair, depending on your profile

If it seeps at the floor-to-wall corner, run a bead of aquarium silicone around the inside corner and give it 24 hours to cure.

Use

Fill to 85 mm with half-strength nutrient solution. Push the pots in until the lugs snap into their grooves and the lip sits flat on the lid.

Change the solution weekly. Two litres of still water with three small plants is slow uptake, and stagnant nutrient goes anaerobic sooner than you'd think.

Remixing

Only the socket interface is carried over — bore, chamfer, and lug profile, measured off the source geometry and rebuilt as parametric solids. Everything else is new. If you want a different pot count or reservoir size, the two dimensions worth touching are the socket bolt circle and the reservoir extrude height. The tub height is set by how far your net pots hang below the lid (55 mm here) plus the water depth you want under them.

Credits

Socket geometry derived from Modular Hydroponic Tower by blove — https://www.printables.com/model/720081-modular-hydroponic-tower

That model is itself a remix of Modular Hydroponics Tower: Ebb & Flow by Beadsworth on Thingiverse — https://www.thingiverse.com/thing:3863771

Thanks to both for the net-pot interface this piggybacks on.