Bubble tip or long tentacle anemone (aka LTA - macrodactyla doreensis). LTA’s live in the sand and can get very large. Bta’s stay on the rocks and split very frequently, so eventually you will have many of them. Both require a mature tank (at least 6 months, a year is better) and coral quality lighting. Be on the watch out for bleached anemones and avoid them as a beginner. No anemone should be white or completely transparent, if it is, it is bleached.