Goldfish tank gravel

Question
Hi Matt,
My question is about gravel for a goldfish tank.  I have an 18 gallon tank with three healthy and happy goldfish.  The largest goldfish has had gravel caught in his mouth THREE times - that I have had to gently remove.  I am searching for larger gravel - perhaps over 5mm - but this is proving difficult to find!  I found this online site to purchase tumbled glass chips.  These chips are smooth and a nice size.  What is your suggestion??
Thanks so much for your help!
Heidi

Answer
Hi Heidi,
Yes it would be the best idea to get larger gravel.  All goldfish love sucking up gravel to see if theres anything edible on it or around it then spit it back out.  Some aquarists have such big goldfish that they must use marbles.  I have seen some of them use black marbles which looks identical to regular gravel from far away.  Any gravel larger than the mouth is fine.  The glass chips you mentioned would also be appropriate.
-Matt-