My mistake, my mistake.

It seems I had my Antimatter confused with mah Dark matter.

Antimatter: https://en.wikipedia.org/wiki/Antimatter

Dark matter: https://en.wikipedia.org/wiki/Dark_matter

Antimass:

I and the Internet have never heard of antimass.

Negative mass: https://en.wikipedia.org/wiki/Negative_mass

Dark energy: https://en.wikipedia.org/wiki/Dark_energy

Dark fluid: https://en.wikipedia.org/wiki/Dark_fluid :

> Dark fluid goes beyond dark matter and dark energy in that it predicts a continuous range of attractive and repulsive qualities under various matter density cases. Indeed, special cases of various other gravitational theories are reproduced by dark fluid, e.g. inflation, quintessence, k-essence, f(R), Generalized Einstein-Aether f(K), MOND, TeVeS, BSTV, etc. Dark fluid theory also suggests new models, such as a certain f(K+R) model that suggests interesting corrections to MOND that depend on redshift and density