Ok so i know goldfish will eat anything they fit in their mouth (ie fish food/ plant life/ real small fish) but will they eat pebbles and if so will they hurt the goldfish. Ive seen mine pick a few up but he seems to alway spit them back out. Is it wise to go with marbles or larger rocks??
They 'clean' the rocks to find microscopic debris to eat. Not harmful, goldies all do it. Helps to keep the gravel clean, but it still means lots of wter changes for them!