Ok so recently I started volunteering at my son's elementary school cleaning the fish tank... when I arrived the water was so green and dark you couldn't tell that there were any fish in it (see photo) - anyways I have worked for almost two months now to slowly clean and get the tank clear (see photo) - so I'm at petco getting some friends for the two black skirt tetras in the tank... because one they are schooling fish, and two the tank was looking sad with just the two black skirt tetras and the other two fish which I am now thinking are another kind of tetras - back on topic I tell this whole story to the woman at petco... she precedes to tell me that I should never have done any water changes (what?!?) and that she doesn't really feel good selling me any more tetras... I enventually got her to sell me 4 more black skirt tetras BUT I AM SO CONFUSED! According to her I shouldn't be doing water changes - I'm sorry but my dad had fish tanks while I was growing up and I've have several in all different sizes and I was under the impression correctly done frequent water changes were what I was suppose to be doing??!?!