Good move. Aside from the appearance aspect, the benefits of live plants cannot be understated.
You can grow the vast majority of aquarium plants without additional CO2. But the CO2 occurring naturally in an aquarium (from fish but much more from bacteria) is not inexhaustible, and the more water movement particularly at the surface, the faster the gaseous exchange occurs (CO2 is driven out, O is brought in) and this can seriously affect plant growth. So removing any "bubbling" devices is advisable.
Light is the single most important factor in plant growth; it is the energy that drives photosynthesis. The intensity is important, along with the spectrum. You can read more on this in the series of articles I authored at the head of this section entitled "A Basic Approach h to the Natural Planted Aquarium," Part 4 specifically deals with light but the whole balance is covered in the series.
What specifically is your tube? Make, watts, kelvin, etc.? Is it full length of the tank? I will hold off on plant suggestions since light is a determining factor.
To the question of the Black Skirt Tetra, yes. We have fish (and plant) profiles here, second tab from the left in the blue bar across the top of the page. The profile for the Black Widow Tetra
[another common name] mentions that the black will be intensified under subdued light (less) and with floating plants, which will replicate the natural environment of this species. When a fish name is shaded, you can click the name to see the profile.
Light again is the critical issue, so we can discuss floating plants more when the specifics are known.