I have a couple of thoughts that I’d like to throw out there.
First of all, good for you for adopting this turtle and doing your homework on how to provide a proper environment. I would love it if you could post pictures of this beautiful big turtle. I see lots of pictures of 3” and 4” turtles on here and not nearly enough of the big girls. Your turtle sounds like it has a great personality, especially considering the lack of proper environment.
You said two things that I have to “throw my two cents in” on…
teta wrote: Since the tank has to be cleaned weekly
You shouldn't have to clean your tank weekly. (although, I'm sure you do right now) When you get yoru new tank, it'll be better. A little tank maintenance done weekly should keep a 150 gallon tank absolutely pristine at all times (assuming proper filtration).
As a comparison, I am only able to maintain 40 gallons of water in a 75 gallon tank and I clean the tank about every 4 to 8 weeks. So, once you have plenty of water, with plenty of filtration, your maintenance schedule gets much easier to cope with.
You also said you have the tank near a window for UV light? That won’t work. The glass filters out the UV rays that your turtle wants, and direct sunlight just leads to massive algae growth. You want to shield your tank or tanks from direct sunlight at all times as much as possible. Aquarium backings on the sides and back help with this. If you don’t protect the tank from direct sunlight, you’ll be cleaning your tank every week!
