Animals including fish and of course dogs communicate with their owners to let them know how happy they are with their surroundings.
You might wish your dog could talk so that you would know how he/she is feeling and also what he/she is actually thinking. And of course this is not the case, you have to learn to read his/her actions, and it can be fun!
A happy dog will be relaxed with his/her whole body. He/she wags his/her tail, and the tail wags his/her whole body. He/she also has relaxed ears, a soft pant, and his/her eyes are soft. You should be able to see that he/she is totally at ease at this moment in time.
Your dog’s genes is an aspect to consider also. His/her priorities will changed based on his/her breed, he/she may feel pure joy, wag his/her tail, bark, grin, and spin in circles. For example, a terrier enjoys sniffing out and playing, a border collie is at his/her best when being directed through an obstacle activity, a retriever is into fetching. When you have identified what makes your dog happy, offer him/her the activity as often as you can.
You are working towards a happy dog, filled with stimulation and contentment.