It's good to hear that it's no longer in that wire cage, and as for it becoming aggressive once settled in, that's normal, it was being itself. At least 9 times out of 10, if a monitor isn't defensive when approached the caging conditions aren't where they should be.
Pet shops rarely keep them warm enough for them to function normally so they seem "tame" at the store. Take it home, get the temps & humidity right & two weeks later you've got a mini T-Rex on your hands. Then you know you're doing something right. They generally calm down as they age but not all will tolerate handling very well.
It sounds like you care about it, if not you wouldn't be here. To be honest, I think you have a lot of reading to do still. And there's nothing wrong with that as we all had to start somewhere. We can't change the past so let's just pick up where you are & move forward.
Plexiglass sides and wire top isn't good for a monitor cage/enclosure. The cage has to hold a lot of heat and a decent amount of humidity. That's one reason the term "enclosure" is used, it encloses the monitor's environment.
There are 3 main types of enclosures used for monitors.
1 - Stock tank (horse/cattle feed troughs) that holds soil substrate, sometimes having a wooden box-type addition on top.
2 - Plywood-type box with the wood either sealed or lined on the inside to protect against moisture, usually having sliding glass doors on the front.
3 - An even bigger wood-framed box with a stock tank on the inside for holding substrate.
While aquariums can be modified for temporary use they're not good for long term. A screen top would have to be mostly covered with aluminum foil, plastic, plexiglass, etc, to hold humdity & heat. Top-vented systems do not work very well though.
There are plenty of pics here, just search the forums for "monitor cage" or "monitor enclosure" and likewise. I also strongly encourage you to search the forums for posts on both species you have, and even some topics involving other species because you'll usually find something relative. There's plenty of good reading just within the 6 pages linked to the main monitor forum index.
The answer to just about any question you have can be found on this forum or a Google search, but there will be times you'll get confused or need an explanation or something. Don't hesitate to ask.
By the way, I'm not one of the top dawgs around here, I'm suckin' hind tit. You know, almost the runt of the litter. There are plenty of wise old hounds around to keep us all on the right trail. Don't lose the scent and don't go barkin' up the wrong tree. Those are my jobs. Hahaha!!!
Catch ya later!
HH
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Due to political correctness run amuck,
this ol' hillbilly is now referred to as an:
Appalachian American