What Is An Observation?

An observation is the action or process of observing something or someone carefully or in order to gain information.
For example, an observation of this tank is that all the plants are green or that the rocks at the bottom are neutral colors.
An opinion is a view or judgment formed about something, not necessarily based on fact or knowledge. An example of this is that I think  the pinkish fish is the most appealing because of its color.
An inference is a conclusion reached on the basis of evidence and reasoning. For example, none of the fish in the tank are aggressive because they aren't attacking each other.  This is based on the fact that in the picture, all of the fish are swimming peacefully among each other.

A good observation would include observations made by multiple senses, not just sight. Observation is important in scientific inquiry because without it, scientists could possibly miss a slight change that could have drastic effects. Inferences have a place in science while opinions do not. This is because opinions aren't necessarily factually based. Inferences, however, are in fact based on evidence and reasoning.