What is this in my overflow

My Tank has been running for two months, in the past week I noticed these in my overflow. They look like some type of larvae, any ideas? 300lbs of live sand, 50lbs of live rock, 1000gph over flow, 1000gph return pump, 30 gallon sump with rock, macro algae refugium, a 500gph powerhead, and floss media.
The back part of the overflow is clear and is the only part of my tank that can get any sunlight through the blinds.
This is in south florida, nothing flying in my home. This is also on my marine tank with a Coral Cat Shark, Snowflake Eel, Nassarius Snails, Emerald and Hermit Crabs.

That's what I thought after just doing some googling, theyre rampant in South Florida. Now I need to figure out how to keep them out of my overflow. I'm renting the home and haven't had any problems with them around the house, but my tank and stand is made of plywood and other types of wood. Cover the overflow and put Hermits or turbos in the overflow to control it?