My comment is a very general one, relating to the whole idea of taking any casual interest or hobby and trying to turn it into a business.
I've tried exactly that a couple of times in my life...not with aquariums...and it always ended up with me not enjoying that thing anymore, or at least not to the extent that I had before. Sure, I've heard all the same tired homilies about it..."Find a job you love and you'll never work a day in your life!"...and similar BS. IMHO, turning anything you love into a chore guarantees you won't love it for very long afterwards.
I do believe that there is some tiny percentage of people who manage to make it work, and I'm happy for them. But overall, if I truly enjoy doing something, I don't want to do it because I
need to; once it becomes work, once you
must do it...it stops being fun.
It's bad enough when you allow a hobby to outgrow your passion for it; we see it all the time with aquariums, where people will either stop doing other things they love because of the time they are forced to spend with their overly-large collections of aquariums...or, just as bad, when they start to neglect those aquariums and they turn into dirty poorly-maintained quagmires full of unhealthy fish.
But when the hobby turns into a source of income upon which you rely...well, that's the kiss of death.
I produce just enough fish that my hobby partially pays for itself. I buy very few new fish...my ongoing aquarium expenses are minimal, the biggest being fish food. I am successful at deluding myself...most of the time...that the electricity consumed is free, and that my time and labour is worth nothing. As a retiree...that's pretty accurate!
But if I woke up tomorrow and decided that I needed more money to make ends meet, I would not even consider getting it by breeding fish, or by "monetizing" any of my other interests. I'd go back to work in my trade. No, I don't "enjoy" it...never did...but I can tolerate it. I didn't and don't expect or even hope for my day job to provide a sense of satisfaction or to fill my life with joy and purpose. That's what hobbies are for. A job earns money, and money pays for the other things in life.