Has anyone ever heard of an FA device that would suction mats of FA using a small gas engine...
Yes; or something similar. However, most trash-pumps have problems maintaining a strong vacuum when their intake is placed on or near the surface (where it often cavitates, and inducts air instead of water - prompting a severe drop in vacuum-pressure when the pump loses prime).
The device that I recall seeing used a high-volume/gas-engine trash-pump that sourced its water from an intake-hose (always fully submerged & primed), and jetted water into a venturi-device that, in turn, created a constant vacumm on an attached surface-skimmer boom - which deposited surface-debris (including algae) into a "filter bag", or an on-shore "collection corral", which allowed filtered water to re-enter the lake or pond.
*not unlike many common dredge-devices*
