Advice needed for 1st timer!

Hi everyone,

My in-laws, without asking, got our kids two turtles. As expected, no one wanted to take care of them. They originally came in a small plastic box.

I immediately raised concerns about their need for a bigger space, clean water, and proper care. Having some past experience with aquariums, I did a quick search to confirm what they’d require. Based on that, I went ahead and ordered this aquarium from Amazon.

I’ve set up a water heater and change the filter once a month. Initially, the water was very cloudy, but after going through the nitrogen cycle, good bacteria have now stabilized it. I feed the turtles outside the tank, and they eat well. I also change 25% of the water weekly and add a sludge remover liquid regularly.

That said, my gut is telling me they might need even more space. What do you think? Thanks in advance!

P.S. my kids 7 and 5 love the turtles and play with them carefully sometimes.