This to me looks like classic Ostreopsis. The almond shape and the lighter tip are pretty indicative. If you want to see it more clearly, you can try dark-field microscopy (a fairly simply DIY that I much prefer over light-field). Also check out this Dino identification bible from Jonathan Begnaud that I always refer to:
Yup thats ostreopsis. Relatively Easy to deal with:
1- Blow the crap out of your rocks and get them floating.
2- use coral snow + bacteria mixed together( TP nitribiotic is what worked well for me)
3- UV sterilizer in the sump: i use a dedicated pump in the drain chamber fir the input and the return chamber for the output.
You will get rid of this ugly in few days time.
I just had them last week and it took 3 day to wiped them clean!!