Fish and similar low-interaction pets offer routine and a calming presence, though with less of the direct social benefit higher-interaction pets provide.
What they do offer
A daily care routine (feeding, tank maintenance) and a documented calming effect from simply observing an aquarium, without the responsibility of walks or vet visits as frequently.
If loneliness is your primary concern, a higher-interaction pet or the community-building articles in our Community & Loneliness section may serve you better than a low-interaction pet alone.