Aquarium Plotter Shows Sisyphish’s Submerged Sand Stripes

Sisyphus is cursed to roll a boulder up a hill for eternity. Pet fish generally content themselves to swimming the same lap over and over in a glass tank. Perpetuity can be soothing, so long as you’re not shouldering a boulder.

[Zach Frew] wants to integrate and automate the boulder on a smaller scale and one that can benefit his aquarium full of colorful Taiwanese bee shrimp. Instead of an inert rock and a Greek, Sisyphish uses a magnet and servo motors connected to a microcontroller to draw Spirograph-style shapes in the tank’s sand.

There are a couple of gears beneath the tank to trace the geometric patterns but they’re clear of any water. One gear rotates about the center of the cylindrical tank while the other holds a magnet and adjusts the distance from the center. Pilots, and select nerds, will recognize this as rho-theta positioning. Despite the uncommon coordinate system, the circular plotter accepts G-code. We love when math gets turned into gorgeous designs, and shrimp love when those tasty microbes get shaken from their gravelly hiding places.

We adore the dry sand plotters that came before, and Sisyphus himself appeared in a LEGO format that made us question our proficiency with the blocks.


16 thoughts on “Aquarium Plotter Shows Sisyphish’s Submerged Sand Stripes

    1. That is really smart and a nice integration in the final result, looks very sleek. Makes me think of a hyped-up magnetic stir rod personally, though I see that apparently sand-pushing robots are a somewhat recurring theme.

      Now I have to dig in and see if the G code is Cartesian or if it exposes the native axes of the unique kinematics here…

      Nice work!

  1. Nice to see the update. If I remember correctly, the last time we saw this project it was still in the dry phase. Good work on getting the aquarium up and running. I made an aquarium out of a gotchagotcha a while back, and I have a soft spot for niche aquarium builds.

    1. I used a poron foam on the bottom. Your intuition that glass might have been damaged by consistent abrasion from the sand is spot on. Sand on glass is also very loud, even in an insulator like water, so the poron quiets the system down.

  2. very nice project.
    nice little bonsai garden in there at the same time would be very scenic and tranquil.
    now maybe modulate a basic spiral pattern with the S&P500, or maybe bitcoin.

    and a caption in the vid “100X speedup!”

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