" Did Mister Krabs had a wife? "... Well, I have thought of that many times and I am pretty sure that the answer is - YES!
You see, he has a daughter and that probably means that he had been married ( in case you are not aware of that fact, his daughter is Pearl, 16 years old ). Since Krabs is... a crab and Pearl is... a whale, you can reach the conclusion that Mrs. Krabs was a whale as well. Adding the fact that Mister Krabs had no problem spending all of his money for his darling Mrs. Puff in the episode " Krusty Love ", you can guess that Mrs. Krabs has D-I-E-D, or that they have divorced. You can also guess that Krabs is a C-H-E-A-T-E-R, but the possibilities of that being true are extremely slim.
What happened to Mrs. Krabs after the birth of Pearl will remain a mystery, but she definitely existed.
That's all - superplanZ