I have recently bought a elite 21ltr starter kit with 2 veiltail goldfish. I have been dogged with problems since the beginning (6 weeks ago). I have never had clear water & the fish have had both fungal and bacterial infections. I am meticulous about my water changes and tank cleaning. I ordered a tetra testing kit but it arrived without the colour cards in it so I couldnt do the tests. The tank comes with and elite stingray 21 filter. Is the filter rubbish? Please help me.