Question

a fish tank has water, rocks, plants, and fish. which abiotic factor is missing that all the living things need to survive?

Explanation:

Step1: Recall abiotic factors

Abiotic factors are non - living parts of an ecosystem.

Step2: List essential abiotic factors

Essential abiotic factors for living things include water (present), rocks (a form of soil or substrate, present in a sense), but sunlight is a crucial abiotic factor. Plants need sunlight for photosynthesis (to make food), and the energy from sunlight is the base of the food chain in most ecosystems. Even if the tank is indoors, artificial light (which mimics sunlight in providing energy for photosynthesis) is often considered equivalent in a fish - tank context.

Answer:

Sunlight (or in an indoor tank, artificial light which acts as a substitute for sunlight)