[oreocookeee]

i was thinking of a hook like this:

\___
......\___
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you could drive it straight into the tetra without worrying where it connects. when you lift it up, the tetra would slide down the incline to the stopper on the end of the hook. this way the position of the tetra on the arm will always be the same without have to control it precisely. the slant would not be steep, maybe about 10 degrees max, so that the tetra wont lose any height.