Hello, I used to have one of those nano tanks.
Lovely looking tank, sleek and stylish with inbuilt filter and little led.
The filter is good and effective but only with the substrate it comes with, the largish ceramic media rocks, I tried this tank with normal substrate and the issue with using normal substrate is that it chokes the filter and renders the filter useless.
However I have seen some upgrades that may work, a sort of ring that goes around the filter and substrate goes on top and around the filter, stops it clogging the intake and thus keeping the water flow to the filter going.
The other issue with this is the little led lights, not particularly good for any plants that requires half decent lights, only the simplest plants like java moss and java ferns, that sort of thing that does not require lots of light may work well.
Lastly, the size of the tank, 30litres, this kind of severely limits what you can stock in here fish wise, a single betta splenden might be ok but the flow and bubbles from top of filter pipe in middle of tank may cause issues for the betta.
I have never kept a betta so will leave that for the more experienced betta keepers to chime in about that.
The only live stock I kept in that tank when I had it for the short while was red cherry shrimps and some snails. I gave up on that tank when found I could only have the ceramic media rocks and not any other kind of substrate at the time, this was a few years ago, so there may have been some upgrades or changes since then but the fundamental design remains the same imho.
These bioorb flow 15l and 30l are ideal for a shrimp only set up to be honest but other than that, not a lot of choice truth be told.