[Omar23]

I have a 7.5 gallon (30 litre) planted tank and would love to stock it with fish at all levels of the water. just trying to get a sense of different stocking ideas. Please help me with this list.
So far i have:
Top level - clown killifish, redline borneo halfbeak
Mid level - celestial pearl danio, other small rasbora
Bottom level - shrimp, mexican crayfish, pygmy cory, maybe neon blue goby

 

[ElleDee]

How deep is this tank? If it's on the shallow side, which seems very likely for a nano tank, there's not enough room to get 3 distinct levels. It's more like 2-ish (closer to top/closer to substrate) with some overlap. You'd have a hard time getting 3 schools in there anyway.

To add to your list, male endler's would fit in a tank that size.

 

[MissCris]

I think in a tank that small you are really looking at only two zones: floor and water column.

If you do pygmy cories, go with corydoras hasbrosus for bottom level, as the other mini cory species tend to spend more time mid-level instead of on the substrate. In a 7.5 gallon though, I think neocardenia shrimp would be a better option so you can save the bioload capacity for more mid-upper level fish.

I'd do a school of very small tetras, like embers, or small rasboras for the water column, or maybe a group of male endlers. I'm partial to my kubotai rasboras personally, as they are colorful, active schoolers and not at all shy, and are small enough that you could probably keep 8-10 in that tank if you went for shrimp as your lower region inhabitants.