https://www.ebay.com/itm/Rhipsalis-Clavata-Jungle-Cactus-epiphyllum-cacti-exotic-succulent-plant/333461507590?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D4ef4c42e6cc14601bfb650f86c428890%26pid%3D100675%26rk%3D3%26rkt%3D15%26sd%3D193266682710%26itm%3D333461507590%26pmt%3D0%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3Aa38a3155-30e8-11ea-ba46-74dbd1801ebb%7Cparentrq%3A7d816f0016f0a12931171514ff917e2c%7Ciid%3A1

Oh man I hate to be a Debbie Downer, but I‘m pretty sure that could be mealies. The mealy bugs I usually see don’t really move at all. Makes them super easy to kill. Sometimes I will just see white cotton fluff and never a bug. Exactly what I see on your cactus. It’s kind of weird tbh because I know there are bugs somewhere laying these fluffy egg sacs. Take some of the white fluff you’re worried about and rub it in between your fingers, if it’s bugs they will leave behind an orange color on your finger. The one I circled red really doesn’t look right to me. See how they’re hanging out in the joints? That is very stereotypical of mealy bugs. This pic of a Rhipsalis from DangerGarden is what ”normal” white fluffiness looks like. Rhipsalis hadrosoma pretty much doesn’t have bristles, very different from your Rhipsalis. Pic R. hadrosoma from Google.

The sans is about 5 years old, the hahni died 😢. I read your comment wrong at first, thought our soils were the same. My sans is planted in 50% sifted, coarse perlit; 25% miracle grow soil & 25 play sand. Yes you read that right. It was the first succlent, so I naively thought ”deserts have sand!!” But it likes it here, so it’s not been repotted in FIVE YEARS! I keep reading not to repot sans until their roots shatter the pot. Probably nonsense, but it isn’t screaming for a repot yet, so I’ll let it go. It’s in unglazed, 6” terra cotta & I keep it year-round in bright, East facing sun. I’m lucky enough to have an East-facing screened porch, so it sits out there all spring, summer & into late fall. I fert regularly w/ MG in the yellow bottle & water about 1x a wk or every 2, depending on season. That’s pretty much it! BTW, this plant came from a pup that I pulled out of my bf’s mom’s 50+y.o. sans by accident - when I was caring for them while they wintered in FL. I thought I was just pulling out a dead leaf, the pup came with it, so I potted it up. It was originally my bf’s grandmother’s plant but she’s 96 & now in a nursing home.

Absolutely. You can confirm that it's not a Euphorbia by trimming a little piece and NOT finding white sap inside.