Hi, musk turtles are great starter turtles, but two would require a much larger tank than a 29gal. One typically should be in a 40gal with two maybe 55-75gal. They would be fine in a 29 for a couple of years but you would need to upgrade eventually. They are also known to be quite solitary, keeping two can be risky with one likely to get bullied, but it can be done while they are juvenile, as adults they are likely to attack each other so be prepared to separate them if they do, which means double the setup and equipment.
The best way to keep two turtles is to mix breeds. Musks and mud turtles go well as do musks and map turtles. All three are similar in habitat and size when grown.
The setup can cost as they need specialist equipment. They need a basking area, they are known to be shy and not to bask but it's crucial that it is provided as they do use it for thermo-regulation on occasion. A basking area is an area out of the water with a basking lamp for reptiles and amphibians. It creates a spot of heat with out lying cooler zones, which they use to heat them selves as they have no way to regulate their body temp. They also require, like every turtle, a UVB bulb which provides both UVA and UVB radiation essential to maintain a good appetite and metabolise calcium for their shells. As well as a heater and very good filtration a they are all messy creatures.
They are best brought as hatchlings and kept in shallow water, you will love their size when young as they can be tiny. They are great to watch grow and learn as they become more friendly with you.
