Mini Slug-like Creatures

[bjmagik]

Hi there,
I have 2 tropical tanks. One being a 2 foot and one being a 3 foot. I have just done a fortnightly water change as usual but in pumping the rocks i have noticed millions and millions of tiny slug-like creatures all through the gravel of the tank. They are similar to the snail infestations that you can get but when i had a close look they were like little slugs crawling over everything. Can anyone tell me what these are and why they have ended up in my tank. Any help would be appreciated. PH, Ammonia, etc perfect.

 

[kpintheshed]

im not sure but are ur tanks clean because bacterial worms can form and also if u could scoop one up and take a pic it would be helpful to identify it