before the entire world jumps on this, ill take a stab at this.
Maderin gobies, although very attractive fish, are VERY difficult to keep. Why? because of their diet. If you do not have a large (75 gal
+) and well established tank, you will be unscuccessful in your attemp to keep one. You will find that they eat the pods
off your live rock.
Most gobies prefer a live sand bed to burrow in, but live sand doesnt necessisarily mean you bought live sand. if you have little bitty critters in your sand, then it is live. ( i am sure there are many articles on this)
gobies you might want to look at IMO
firefish - Nemateleotris helfrichi or decora
heck there are many and a good place to see pics and choices is www.Liveaquaria.com
if they put the "expert" disclaimer on the description, they are serioius about it.