The filter media in our Biofilters is 17 feet below the filter deck under 10 feet of water, so grabbing a sample of filter media is tricky.  This spear stabs into the surface and pulls out a good sample for analysis.  

You will need a 3-4 foot length of 3/8" threaded rod with one end sharpened on a grinder.  Different diameter can be used but the scale will have to be adjusted so the center holes of the fins and tips is slightly smaller than the threading.  

You will also need a length of paracord, I have included a picture showing how to make an adjustable wrist loop.  

For durability these are meant to be printed in TPU.  3 perimeters should be enough to get everything 100% solid.  The fins may benefit from an outer brim since TPU really likes to warp.  

The star-shaped cone is better at going into compacted media (a filter with longer run hours).  We use a small rinse bottle to get the media out into a beaker and take multiple samples around the bed for a composite run in the lab for ATP testing mostly.