I would say that you need to take all shop advice with a very large pinch of salt! Never forget that, unlike the members here, shops have to sell you stuff and make a profit, and that can seriously compromise the standard of the advice you get.
You really should get test kits of your own. Murphy's Law will tell you that the time you need to test urgently will be at 10:30 PM on a Saturday! If you do get a shop to test for you, you must get them to write down the actual numbers; 'fine' is of no use to anyone, tbh.
Making sure your water is good, and that your tanks are properly cycled is far, far more urgent than any fry coming along.
We don't recommend the use of hatcheries or breeding boxes; they're too small for the mother fish to feel comfortable (which can lead to them either holding onto their fry or aborting them) and too small for the fry to grow properly.
If you have some dense planting, you'll have plenty of fry survive. The parents won't search out and eat every fry, and if the fry are well fed and have plenty of good clean water, they grow too big to eat within a week or two.
If you bear in mind that every female can have at least 20 or 30 fry every 30 days (and can store sperm, so can continue having litters even if there are no males present) and that the fry themselves can start breeding at around three or four months old, you'll realise that your fish population can spiral out of control very quickly.
