"And Katie had always been a funny sleeper. She couldn't get a good, deep, restorative sleep and wake up fresh the next day. She was always fatigued which she put down to her sleep, and she also didn't see much improvement during the health kick."
At the same time, the pair were reading about health and fitness when they stumbled on the "massive role" sleep plays.
They fell into a "rabbit hole" of research, eventually discovering the concept of blue light overexposure and how it can disrupt your body clock.
In a nutshell, natural blue light comes from the sun and helps to determine our sleep-wake cycles. But artificial blue light comes from screens – including televisions – as well as light bulbs.
When we are exposed to too much of it, it can throw out our circadian rhythms, according to a report on blue light by Royal Society Te Apārangi in New Zealand in 2018.
As a result, blue light blocking glasses have emerged which claim to filter out that harmful light and boost the wearer's health.
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But when Andy Mant bought a pair online in an attempt to fix his sleep issues, they were "hideous".
"They looked like ugly safety goggles – honestly I thought Andy was mad, and there was no way I'd be caught dead in them even in the house let alone going out to dinner," Katie Mant said.
They realised there was a gap in the market for products that actually looked good, and launched their own brand, BLUblox, as a "side hustle" in 2017, often working 16-hour days.
They used just A$1500 which they had received from work bonuses in their roles as recruitment managers, which went towards a basic website, their first products and packaging.
While they kept their day jobs, the business exploded and they eventually quit work to focus on the company full-time last September, even hiring their first staff member.
In 2019, BLUblox's revenue was A$1.5 million – and it's on track to double that to A$3 million this year.
But for the first two years, the couple didn't take a cent from the business, instead investing everything right back into it.
"It's all too easy, when the money starts coming in, to spend it thinking, 'I'm a millionaire. I can live the rich life now.' Then you have no money to invest back into the business," Katie Mant said.
"We didn't start taking a salary until a month after we'd left our full-time jobs after two years, and then we took a very modest salary, just enough to pay our mortgage and cover everyday costs like food.
"We put the money the business was earning back into marketing, educating, sponsoring, buying new products."
The Mants said they noticed positive changes in their sleeping patterns soon after starting to use blue light blocking glasses, and that they believed insomnia was so widespread these days because we live in a world that's "devoid of darkness".
"Our cells need both light and darkness to function properly, but we've now invented mini-suns that live in our houses in the form of digital devices and they trick our brains," Andy Mant said.
"It's not how we evolved to live and it's a major problem that's only going to get worse unless we educate people."
The couple said it wasn't a "fad" but rather an important health movement that was only going to grow in popularity as word spread.