[mnemenoi]

Embers are in my opinion the largest of the teeny tiny fish. Ruby tetra are just a bit smaller and then Chili rasbora, to the sparrows being the smallest I have had. The Embers are the bravest and the others are crazy skittish. CPD's and Chili's in a densely planted with anything hide all the time. They are literally under the plants and occasionally I see a flash to let me know they are indeed alive. They are all quite fast, so would be able to avoid Buck unless they are ill. I personally would advise for more embers or try some rubies as I have had them in that same tank without any real issues. Top water fish are tough in such a tight tank and a betta. Usually I recommend Eques pencils, but in your case I'd avoid them as they are slow. Psuedomugils might work again if the betta was not in the picture. pygmy cories would work and actually mostly swim mid water. Otos are a good idea if feeding is watched and targeted if the consume all their focus algae. I have also had decent success with kuhli loaches in a similar set up. Good Luck and let us know what works and does not

 

[mnemenoi]

With the footage up top its just small for them, a long 12 gallon maybe... that's why eques pencilfish and African butterfly fish are useful. Top water fish with little movement, but the betta would shred slow movers or at least harass them incessantly.