Filter cup STL generator
Filter socks work until you have to wash them. A filter cup drops into the same 4″ or 7″ holder, holds disposable floss instead, and goes straight back in once you’ve thrown the dirty floss away.
Free to design · 1 credit per new design · Watertight STL + 3MF
How it works
Your numbers, not ours.
It’s sized to your holder, not to a label. “4 inch” and “7 inch” name the sock’s ring, and holder holes vary, so measure the hole with calipers and the neck drops in with your lid clearance around it. The wrap core is a perforated tube inside a slotted cage: wrap a strip of filter floss around it, and water has to pass through the floss on its way out. The floss cup is the cage on its own, for stuffing. A band of windows under the neck is the overflow bypass, so a clogged cup spills into the sump instead of over the holder.
What you can tweak
- Wrap core or floss cup
- 4″ or 7″ nominal, or a measured hole from 50 to 200 mm
- Rim lip 4–15 mm, for holder plates 2–20 mm thick
- Length 60–350 mm, wall 1.6–5 mm, perforated or solid bottom
- Diagonal slots, vertical slots, holes or a diamond grid, openings 2–10 mm
- Overflow bypass windows 8–30 mm tall, or off
- Pad gap 4–25 mm around the core, with pull tabs and a centering ring
Print tips
Print it right the first time.
Measure the hole
Measure your holder’s hole with calipers instead of trusting the 4″ or 7″ label, type it in under Custom, and print the Fit-Test Coupon so your lid clearance is right.
Swap the floss every few days
Floss works because it clogs. Toss it every few days and before the water starts reaching the bypass. The wrap core tells you what strip to cut.
PETG or ASA
A cup sits in saltwater and hangs from its rim, so print it in PETG, or ASA under lights. Skip PLA.
FAQ
Filter Cup questions.
Measure the hole in your holder with calipers and pick Custom. The 4″ and 7″ sizes are nominal: those labels name the sock’s ring, and holder holes vary.
A perforated tube that sits inside the cage. You wrap a strip of filter floss around it and ReefCAD tells you what size to cut. Its floor is solid, so water has to go through the floss, and wrapping gives you more filter surface than stuffing a cup.
Every few days is a good start. How fast it clogs depends on your tank, so change it sooner if water is reaching the bypass windows.
Yes. The rim slides in like a sock ring. Measure the opening across and use that as the hole size.
A band of big windows just below the neck, above the floss. When the floss clogs, water spills out through them into the sump instead of over the top of the holder.
Yes. The cage and core both print bottom down with the open top up. The rim’s underside is a 45° flare, and the openings have pointed tops. In Wrap core style both pieces come in one file, side by side.
PETG for most tanks, or ASA under strong lights. Skip PLA for anything that lives in saltwater.
More parts
Same fit, different job.
Stop buying racks that almost fit.
Your tank, your plugs, your printer. Design it in a minute, print it tonight.