fatbear's mountian building diamond goby

[fatbear]

okay so i have this little diamond goby (see exibit) who of course is always sifting through the sand....(cute little bugger)....but i have noticed that in the middle of the tank he is attempting to dig a trench of some sort....he scoops all the rocks up in his mouf and piles them up...so far he has a 2" pile started....I don' t know what this behavior is...perhaps one could let me know......

 

[fatbear]

i know the gobys burrow/sand sift....but he puts his belly on the sand and swims real fast...which leads to a cloud of dust in the tank....and one tired little goby....

 

[yellowtail]

they like to move sand around.thats how they got the name sand sifting goby.(nick name)