my tank has been establish for about a year I bought it about a 2 months ago since then I have been trying to get my Nitrate below 20. I can never seem to do it I change my water about every three days usually take about 10 gallons out of my 55 gallon hexagon tank. of course I am cleaning the bottom debree. right now I have a box fish 2 clowns 3 damsels and 2 starfish everybody seems happy I am running a fluval 304 with a protien skimmer any ideas