I am sorry I didn't see pictures or ask what plants you had before but unfortuntaley none of them are aquatic plants. I get ahead of myself sometimes and I had to learn the same leasons about non-aquatic plants. I had hedge I my tank for 3 months thinking I could save it but it eventually it died and made a mess. They will grow for the first couple weeks but they melt and rot son after.
Top one is Monda Grass
Middle one is Dracena sanderiana
Bottom one is Brazilian Sword
All of them will die, rot and pollute your tank. Sorry. This is also the main reason they are covered in algae. They are dying and the algae is feeding off them.
As far as I could tell the other plants, the aquatic ones, seem to be doing ok and not covered in algae, right?
Look at this link for future plants to make sure you are not getting ripped off by your LFS. My LFS sells them all and until I actually asked they would not tell me they were not aquatic. The good thing is they all make wonderful houseplants. I have aluminum plant growing on my windowsill right now and they are really cheap.