A good source for pebbles for use as medium would be a pet-shop where you can buy pebbles for aquariums, the attendants should know what the effect the pebbles have on the water.
(you; can buy; pebbles; for aquariums; L:a pet-shop) (the pebbles; have; L:on the water) (the attendants; should know; what the effect the pebbles have on the water) Context(the attendants should know,List([105, 131))):(A good source for pebbles for use as medium; would be; a pet-shop where you can buy pebbles for aquariums)
the attendants should know,List([105, 131))
you the pebbles the attendants A good source for pebbles for use as medium
can buy have should know would be
pebbles for aquariums L:a pet-shop
L:on the water
what the effect the pebbles have on the water
a pet-shop where you can buy pebbles for aquariums