usually i have better luck attracting minnows with lights that float on the water or even coleman lanters hanging out over the boat. the setup i use
has two lanterns and two of the floating lights occasionally i will drop one of the submersible lights and usually on the dark side of the boat. another thing is the type of minnows in your lake, shad or shiners are the minnows we usually draw into the lights sometimes we use one of those umbrella seins and draw it up around the minnows for bait