I have a bubble gum digi coral that was doing great in my 25 gal. It is currently my only coral and It had all of its polyps opened and was happy, but my nitrates were at 40 ppm. I added some chaeto to lower them and did a water change. after I did the water change my nitrates went down to 26 ppm but my coral completely closed all of its polyps. I checked my alkalinity to make sure it was good and everything was fine. Im actually really confused, i thought i was supposed to have nitrates under 10 ppm for corals to thrive, but this one seems to get mad if it is under 40. My test kits are all good and they are accurate. Could it be that this coral likes dirty water? and if so could i add other corals to the tank? or would they die?