Did you know fantastic help is an anagram of Planet Catfish? This forum is for those of you with pictures of your catfish who are looking for help identifying them. There are many here to help and a firm ID is the first step towards keeping your catfish in the best conditions.
I can't say whether it is margaritifer, but H regani has white spots - on a deep black body when grown. I'd guess this beauty is at least 25 cm - 10 incehs, and a H regani would be as described.
Where does it come from? H regani is quite a southern species (Rio Uruguay)