hello everyone , i have a 400gal(1600lts) fish tank with 5 pacu(16inch each) 1 aligator gar (25 inch),1 clarias 4 tinfoils and one jaguar catfish(15inch) . i found a tiny worm on the glass , it was thinner than a hair and like 3mm long . it was a bit transparent . i removed it and decided to clean up my fish tank by removing 80% water . but i noticed more . there was a lot near the filter . i went to the fish store to inquire , they told me its the ecosystem and that might happened with the biological filter . i dont know what to do ? any advice for me please .
...I can't imagine 80% waters change you should have consulted here first at least before you did that.