Need Help with Fox and Bubble Coral

[Slyguy00]

My bubble coral has a mind of its own. Somedays its huge, other days its fairly small. I dont think its anything to really worry about unless it looks like its dying. When they get rid of there waste they shrink up and kinda look like they are dying to. And i dont really feed my bubble anything, it just sorta takes stuff outta the water that i feed my fish. It has probably doubled in size since i got it and i keep it in high light high flow. Good luck