I have never bought rats from a pet store before. I bred my own mice and then rats, from the get go. I vaguely remember buying a few from a breeder while I was waiting for mine to grow. I can't even imagine how much it would cost me to feed all my reptiles now if I didn't breed my own rodents. I could easily go through over 100 rats a week in the summer. I haven't even bred anything yet!
How many tubs were you running with 800 rats? I wonder how much ammonia gives you ammonia poisoning...... I have around 800 rats at the moment, including younger ones I am growing up for breeding, and am keeping them in a double garage with only 1 small window and the gaps around the garage door, for ventilation. Even when I leave it a month between cleans, it doesn't smell badly of ammonia though, just rat smell. Only my grow out tubs get pretty pongy , but that is because there can be 60-80ish in each giant drawer. My garage looks like a maze now with rows of rack and only just enough space between them to wheel up the food bins and pull out the tubs