Heard from alot of my asian customers bristlenose plecos are best for rays. Alot of ray breeders we know use these in there ponds for alagae control. Best of luck
As said, everyone has a different story. I've kept a rhino pleco (now about 10in) with my rays for 3 years without incident and a king tiger for quite some time as well. Maybe I just lucked out but I've always kept rays and plecos together without incident.