Questions - Need some input

i have been having trouble with my skimmer its a seaclone 150 i know its not the best but its what i got for now the prob is i just reacenty started my150g i started in my 30g i have had the 150g up with live sand and rock for about a month so last week i added my fish and coral and the skimmer because i was using it in my other tank so for the last week i have been getting micro bubbles and i cant get rid of them why why i can not for the life of me figure out why and when the bubbles slow down ...

i am thinking about building a sump for my 150 gal tank i will be converting from fresh water to salt water, fish with coral i am just wondering where i could find plans on how to build one out of a old spare 30 gal tank i have. i do not know anything on how to do this i mean i have been looking around the net but i cant seam to find any plans on how to build it i need to know what size pump, how to build a overflow or should i just buy a overflow please HELP thanks