Christopher Watts, 33, has been arrested on suspicion of murdering his family just one day after he begged for them to return home.
Shannann Watts, 34, and daughters Bella, four, and Celeste, three, vanished on Monday.
It has been reported the family had tens of thousands of dollars of credit-card debt and that Mrs Watts suspected her husband was cheating on her.
The oil and gas tanks their bodies were reportedly found in had been nearly full when the corpses were dumped, according to local media.
Their bodies were stashed in the tanks at the petroleum company where Mr Watts worked to conceal the smell, sources told local journalists.
Mrs Watts was 15 weeks pregnant at the time of her death.
After his family was missing, Mr Watts told reporters he had desperately tried to contact his wife.
Mr Watts said: ”I called her three times, texted her three times […] I figured she was just busy.
“I hope she’s somewhere safe right now and with the kids.”
Heartbreaking social media posts from earlier this year show Mrs Watts lavishing praise on her husband.
In one Instagram update, she shares a photo of the pair smiling into the camera as Mr Watts drapes an arm around his wife’s shoulder.
Mrs Watts posted: “Happy Husband Appreciation Day! I couldn’t imagine a better man for us. You spoil us with love an attention!
“You put up with 3 impatient, demanding women in the house. You Work so hard everyday to provide for us.
“I love you so much and so grateful you hung around when I tried pushing you away in the beginning!”
Authorities are expected to file charges against Mr Watts, who was fired from his job on Wednesday, the day he was arrested.
He is next due in court on Tuesday.