Staring at the background, scrolling the pics and full of questions on how you created it / what it's made of until I found the DIY build thread LOL . VERY NICE!
A single 40w T12 is really low light energy so plants will be limited and extremely slow growing. Is the sand/soil sub about 2" total depth? There is a thread on the forum listing low light plants that is a great reference.
The plant you've added from work looks like Blyxa which has done well here low tech surprising me with good (but slower) growth on 2 non CO2 injected tanks.
This is my lowest level of lighting maintained here.
29g tank, 29 3/4" height (75g should be 21"). Single F15T8 plant grow bulb.
This is 3 months growth.
Crypts, Anubis, Java fern, Suesswassertang, Dwarf sag
No algae issues and really slow growth but the tank looks good for my needs requiring almost no maintenance.
More plants are added here right off using soil as a base along with floaters. The cloudy appearance will clear but in an empty tank it takes time.
Could the background be dusting into the water from the first fill on the tank?
With low light and a soil enriched substrate the tank would be near zero on maintenance demand.
I think your off to a great start, just need to decide how much light you will ultimately run on the tank then load it with plants.