My tank is cycling and there is some weird brown stuff growing RAPIDLY on the sand that looks like its been burnt- i figure its just algae or bacteria so im not so worried. But theres within the last hour been a lot of like little lines on the sand. I think they might be worms or something? Theyres probably like 50 of them (just like a millimeter) in one specific area that all look like dead lines (theres no obvious features like eyes or anything). I got some coral from a tank that had flatworms- but an hour before i got them a little bit of an overdose of flatworm medication was applied and i saw the results. Could they be flatworms? Or are they just part of cycling or the what im starting to think algae bloom.
can anyone help me out? because i dont want to have flatworms before when i add my first fish (a week from today)

I merged your first 2 posts.
Thanks!
Ken