This is my first attempt at a hydroclone. The basic idea is similar to many bag-less vacuum cleaners, the water is forced into a cyclone then through a harsh bend at which heavier objects sink and lighter objects exit through the top.

I tried three designs (all attached). They do work however it does not work well with separating algae which is what I wanted it for. It works really well getting solids from water.

It was designed so that a 15mm plastic tube is attached to the inlet on the side, a coke bottle taped to the bottom and the water exists from the top.

The design with the cross on the bottom is my final and best design so far.