how to add new sand to tank

[frezel]

i have crushed coral in my tank and its been there for 10 years and packed with life snails starfish and mysis, so tiny you can barely see, but through the years since the pieces are pretty coarse coraline has grown on it and has given the bottom of tank a nasty appereance and want to siphon some out and add some fresh clean sand.

How do you propose that i siphon out the top layer of nasty sand with out removing to many good creatures and such?

 

[Dubbin1]

You say first that you have crushed coral then you say you have sand???

 

[frezel]

remove some of the coraline covered crush coral and replace with fine white sand