Hi, I absolutely love my Edge tanks, have had 6, (2 -12G).
Presently I run one 6.6G 23L as a SW Nano tank and a glass only 6.6Grunn with SW MacroAlgae as a storage to hold the extras.
The FW tanks are running now are a 6.6 and a 12G.
In the 6.6G I have a group of Chili Rasbora Boraras Briggitae.
Phoenix - Boraras Merah or Strawberry - Boraras Naevus, would all be fine in there (after it is cycled).
Mini Anchor / Moth / Asian / Stone Catfish - Hara jerdoni, are often hiding but a little group of them is fine for a small space.
You can do Dwarf shrimp, Neocaridina or Caridina. Many kinds to choose from. Try and find locally bred Cherry shrimp (Neocaridina aka Neos) as a nice easy starter shrimp, as you would know they do well in your water.
But there are other colors and you might prefer them.
Ramshorn snails are nice. There are clear, spotted, blue-ish/blue-grey, tan, bronze, brown, red, grey, black, white-ish shells,
with red, orange, peachy, coral, pink, tan, black, grey, brown body.
LOL, lots of options!
Biggest thing to remember is to keep a small cup/container to scoop out water, and a quart/liter to half gallon/2 liter pitcher/container for holding removed water, handy and a towel, when you want to move something around inside the tank.
Because you will inadvertently go to move something and end up with a water over flow~!