Hi guys, I'm just new to this cool site, aswell as to the hobby. I have a 20gal saltwater tank in my room that's been running for about 1 month and 2 weeks now. It has 19lbs of LR, 13lbs of LS, an airstone skimmer and no sump, with just an overhead filter and foam in it. My livestocks are, 3 fishes- (1 small mimic tang, cardinal and small fox face), 3 feather dusters, 3 mushroom coral and 1 leather coral. My problems are, first, my mushroom corals are starting to peel its polyps from the liverocks where it were attached, and the remaining polyps were not expanding fully. I don't know if its was due to the moderate water curretnt they were receiving from the power head. Some of the polyps were now scattered on the sand bed. Also my leather coral is not expanding and has a brown like stuff in its body. Second, I have an outbreak of Diatoms in my tank, my phospate level is 2.0mg/l. I do a weekly 10% water change, but still the phosphate level remained the same. Third, I have a high Nitrate level which was 80mg/l. I did 50% water change, hoping that the Nitrates level will go down. After a day, I test again the the nitrates level and is now 10mg/l. This was supposedly good, but after that water change,the ph level dropped from 8.2 to 7.4, where supposedly it will retain its ph level? Do you think the high Nitrates and phosphate level got something to do with what's happening in my mushroom and leather coral now? Do you think I need a sump to a have better filtration and exchange of gases for more stable ph level? Can my nano reef still have the chance to have a stable water parameters even without a sump? Need help badly...My water parameters now are: SG-1.021, Amonia-0, nitrates-10mg/l, phosphate-2.0mg/l, Ca-160mg/l, ph-7.4, temp- 26C. Lighting 4 x 24watts T5.I dont have a test kit for nitrites and alk.