Massive galaxies at high-redshift (z>2) are thought to grow via pristine cold
gas streaming into dark matter halos, although such cold streams have not been
observed. At the same time, feedback processes from stars and central black
holes regulate stellar mass growth, and can impact the circumgalactic medium
(CGM) by way of feedback processes. Lyman-alpha blobs (LABS) are large (10s -
100 kpc scale) diffuse emission-line nebulae that could either be the
signature of cold gas accretion, with T~10^4-5K gas cooling primarily via
Ly-alpha, or evidence of feedback from young growing galaxies in the CGM. In
either case, LABs offer insight into the complex interface between galaxies
and their surrounding environments. We present new SCUBA-2 observations of
LABs in the SSA22 protocluster at z~3, providing the best constraints on their
sub-mm properties yet achieved. We show that statistically, all LABs have some
level of sub-mm emission, tracing dust-obscured SF and AGN activity, and this
provides new constraints on LAB formation mechanisms and the interplay between cooling and feedback in these early galaxies.