Blob filters can be invoked *only* using API (or more precisely
using BPB), either called "by hand", or generated from Embedded SQL.

Declared blob sub_type in database is just advisory value
(pretty much the same as segment size).

I have not used IBObjects for a long time, so I have no idea
whether calling blob filters is supported.
It is not possible to call blob filter via pure SQL or PSQL.

Ivan