It's great you're trying out something different, but since u have an existing UGF, it would be better to stick with it. If you want better filtration methods, why not combine both systems UGF and a hang on or top filter?

Both hang on and top/overhead filter is different. A hang on filter literally hangs on the side of yr tank creates a waterfall cascading back into yr tank. It's good providing surface water movement thus creating more oxygen for your fish but lousy in terms of cultivating nitrifying bacteria as waterflow is too fast and there's limited space for bacteria colonisation.

A top filter (comprised of a rectangular box and a power head submersed in water) sucks up a lot of muck quickly bypassing the filter wool and charcoal placed inside the top filter before passing water out back into yr tank. It cleans very well while providing chemical filtration, but also not fantastic for nitrifying bacteria. If you're worried that these tetras get sucked up (usually doesn't happen unless yr power head suction gaps are large and very powerful), you might want to use a green mesh and tie it round. Anyway, these tetras got brains and prob won't swim round that area!

However, with both UGF and either of the other filters, you can be assured of getting maximum filtration for your tank not to mention clearer water and healthier fish. Though a bit more work (cleaning 2 filters) but in the long run, gives you satisfaction having happy and healthy pets, isn't it?