From a visit last week, a lovely chat with one of the keepers there confirmed that Blijdorp is now the only successful holder of goose barnacles (Pedunculata) as they have now kept them for over 4 months, which is apparently a record (?) They are unsigned in the small tank opposite the pacific kelp forest tank and their filtration systems and water pumps are connected to said kelp forest which allows the goose barnacles to have a functional filter feeding tank without the risk of fully polluting the water in there (i believe thats how it works, anyways)
I wasn't aware these were difficult to hold, as I've seen them before in Ecomare. I believe these are also the same animals that were taken off the back of one of the seaturtles that washed up.