Effect of extremely hard water on marine life?
Hard water helps in direct and indirect ways. 

Indirectly, hard water plays an important role in regulation of pH. Respiration and other physiological activities release substances into water that change the water pH and the ions that cause hardness act as buffers and help maintain pH.

Directly, they determine the ease with which osmoregulation occurs. The harder the water, the lesser the influx of water. So the fishes act like an open system and are influenced by the surrounding water.

There are very few fish who absolutely need soft water to survive.
Since your pH and hardness are pretty low, it allows you to raise multiple fish from South America. You could do tetras, dwarf cichlids and New World cichlids, Plecos as well.

Potentially discus and altum angelfish as well if you're up to the huge challenge.

However, livebearers will not tolerate this type of water. That goes the same for African cichlids.

Otherwise hard water is completely fine for marine life and other aquatic species.

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Hope this information helped!

-Sartoaster