Need technique for creating Coral runway.

this is in 1/48 or 1/72?

if it is 1/48 you could try using model railroad ballast, they have it in varying colors (hobby lobby or a hobby store) but from memory it would be about the right size. They have different grades of it too so there is a bit to pick from...

Thanx tho9900, there is always someone here willing to help.

how about fine kitty litter? couldn't that be used?

Go to any store that sells aquarium products and you can get the real thing. Crushed coral is commonly used in aquariums for modifying the water chemistry.