hi. i bought a 10 gallon fish tank about 3 weeks ago. needless to say, this is my first aquarium. in the beginning i did everything by the book, and everything was going great. now i'm rolling around my 3 week marker here and my nitrite levels are way up. i've done a 25% water change just the other day, and i'm doing 10% changes evry other day to try to get the nitrite levels down, but it's not working. i went to the pet store the other day, and the lady there suggested that i try a better filter so i did. now my water is murkier, and there's some kind of buildup thats on the inside of my tank walls that i just noticed today. i've been reading up on some of this, but nothing seems to give me the answer. i have 2 platys in there and they are sometimes frantically moving about, but there are no other visible signs.
are these normal signs :( of new aquariums or am i doing something wrong?