Please help me to identify these bugs I just discovered flourishing in my tank. I had 6 congo tetras, 2 buenos Aires tetras, 1 emerald cory, 1 bristle pleco, 2 ghost shrimp, 1 brown mystery snail and 2 zebra snails. In a 45 gallon tank I've had this tank for 3 months with no issues I cycle my water 40% every 2 week's the tank stay relativly clean looking. I feed my tetras once a day fish flakes and and pleco algae wafers every other day, and occasionally feed my fish live blood worms from a local pet store. Last night one of my congo tetras that I had maintained and grown well for months died. The next morning I notices my zebra snail at the water surface half submirdged. Looking closer in the gravel I noticed the blood worms from one week ago still living and running from the light but as well thousands of little insect looking idk what they are. As well there was what looked like a 3/4 inch size flat worm transparent with a brownish grayish color and you could see what looked like a yellow colored skeleton structure. It's head was not spade shaped. I don't have a good picture yet of the worm until I see it again. What should I do? What are they? How come they just appeared after 3 months?(only thing new ocasitnaly being introduced live blood worms from pet store) Here is a video of the small specks I noticed.