Adequate light for "low light" setup

[NeptunesNeighborhood]

Hi All,

In my rack design, I need to integrate lighting. Essentially, what it boils down to, is I need 1x 24" fixture to run perpendicular to back-to-back 20L tanks. I will be doing this 4 seperate times.

What fixture would be recommended? I'm thinking 2x T8 will be fine and I'd like to mount them to the cross-beams, however I'm not sure if that would be sufficient.

(It's low light, soft water, planted apisto tanks.)