I would cut some holes through them for stakes of boo.
they are small pvc spools ,of a couple different lengths, I wired tyed two two three together and weighted them ,drilled holes for air to escape,
I would cut some holes through them for stakes of boo.
With the narrow bases and no floats up top they would be prone to falling over. Would be tempted to add two 3` long pieces of 1" PVC pipe and wire it together in the middle, spread it to 90 degrees and screw it to the bottom of the stack. Might be tempted to also add some "branches" (cover?) on the bottom spool to attract minnows, insect larvae, ect...