I've never had any success with them, but not out of my own fault. When working at the LFS, my old manager would occasionally get adventurous with ordering. The few times we ordered ritteris, they all arrived it utterly dismal condition. They would all turn to a pile of goo within a week of arriving, no matter how ritteri friendly of conditions. We just stopped even bothering. It wasn't worth the cost both ethically and financially to continue to order something that just consistently arrived looking like Delta Airfreight had placed soccer with the box (when other anemones, corals, inverts, or fish packed in the same box came in awesome shape).
They're really difficult to keep, requiring a very large tank, pristine water, excellent flow, and good lighting, too. Out of all the anemones, ritteri's are among some of the least beginner friendly. They ship terribly and often quickly waste away in reef tank. Even more experienced hobbyists can have issues with them. I've only ever personally seen but a few kept in good shape in captivity (one of them, oddly enough, was at a restuarant known for serving excellent seafood).
If anything, I'd recommend sticking with the long tentacle. Much easier on an anemone to keep. Much, much easier and more forgiving that a ritteri.
