Is this tank big enough for a goldfish?

It is a desktop tank, so it suits one small goldfish or a few tiny fish at most. Goldfish grow large and produce a lot of waste, so a bigger tank is the better long-term home.

Does it come with a filter?

Yes. The tank has built-in filtration, so you do not need to buy a separate filter. You still need to change the filter media and do partial water changes.

Do I need a heater or light?

No heater or light is listed. Goldfish and other coldwater fish do fine without a heater at room temperature. A light is useful for live plants and for seeing the fish.

Is plastic safe for fish?

The maker says the tank is free from high-concern chemicals. Rinse it well before the first fill and cycle the water before adding fish.

Empty and rinse it with water only. Skip soap and harsh cleaners, which leave residue that harms fish. Use a soft sponge so the plastic does not scratch.

Is it good for a beginner?

Yes, for a first small setup. It is simple and self-contained, but small tanks swing in water quality fast, so test the water and change part of it often.