thanks for all the comments...
it is a small tanks. only 60cm*45cm*45cm, roughtly, 24-inch
i reuploaded the pic. and i found that the ie browser display the pic color inproperly(more yellow). if you wanna see the difference. save it and compare...
and does anyone konw how to lower the PH...i tested it today (3 times)..it was terrible..12+. and the hardness is also very terrible.....