We bought this tank from someone who had a shop. We have nitrates at 80 and phospates .5. We did a water change on Wed. How often is it possible to do water changes to get those rates in proper order. Also we have loads of particles that are floating around and don't seem to go through the filtration system. We have had this tank for 2 weeks today. I feel this tank was not very well taken care of and the sand may be dirty. Can you use a the same thing you use to clean gravel to clean sand? Your help is appreciated.