If all the stuff came out of an existing tank, you've just disturbed the nutrients. What I would do is add some turbo snails, keep your skimmer clean (you have a good skimer, right?) and some larger frequent water changes. I'd also use RO (purified) water over treated tap water. Never sure what comes out of your tap.
Keep some carbon running, replace every few weeks. Lots of areation to keep pH up, O2 high, and you should see some improvement. Covering your tank with 6l poly makes it hard to view, which is likely why you got the tank in the first place!
It's normal to get this, don't worry a lot about it. Follow the above, you should be good in 3 -6 weeks.