What kind of baitfish is this?

[DanC]

There are tons of these in the lake I've been fishing. Can't figure out what they are

[BiteFiend]

Looks like minnows. 

[DanC]

What kind of minnows?

[BiteFiend]

Tough to tell for sure because of the shadows in the picture but I would guess common minnow. 

[Penguino]

Fathead Minnows

[Jonathan Evans]

Those are fatheads.

[WRB]

Could Creekchub also.

Tom

[Turkey sandwich]

Kinda tough to be 100% from the pics, but those look like fathead minnows.  

[WIGuide]

I would agree that they look like fatheads.

["hamma"]

looks like smelts to me, what lake?

[HeavyDluxe]

Not sparkly-silver enough to be smelt.  I agree with the fathead voters.