My apartment complex has a tank size limit of 10 gallons too but that hasn't stopped me from putting in two 10s, a 55, 90, 100, and 240 (and to top things off, its an upstairs unit lol).
They did an inspection a few years ago when I only had the 90 and a few 55s but it was still a pita cuz I had to bring the fish to a friend's house and hide the tanks in my closet. They came to install carbon monoxide detectors a few months before I got the 240 but it was just the maintenance guy so I left the tanks up and all he said was woah what kind of fish are those

I doubt that's all he would say after seeing the 240 but I'm kinda looking for an excuse to move anyways so it's not a huge deal if they find out (as long as nothing floods the complex first... knock on wood). Luckily the floors are concrete or I wouldn't even consider having that much weight up here, but I doubt renters insurance would cover a tank blowing out so Im resealing the 240 next week to be safe.
That sucks they saw your setup tho, u should've hid them before the inspection lol. They have to give at least 24hr notice before even knocking on the door (at least in CA). Not much u can do now that the property manager knows other than move or sell the tanks and get a nano

Then again, if it's not specifically written out in your lease u may have a leg to stand on in court. But if they're making a big deal about it u won't be able to change their minds so it depends if u wanna take things that far