Key to Heleopera species
| 1 | Symbiotic algae present (mixotrophic species) | H. sphagni = H. picta |
| – | Symbiotic algae absent or impossible to determine | 2 |
| 2 | Shell small, length < 80 µm (50-75 µm). Shape like a long, non-pointed, egg, but quite variable, sometimes with isolated small mineral particles. | H. sylvatica |
| – | Shell larger, usually > 100 µm | 3 |
| 3 | Shell often pink or wine-red, with orange-yellow lips. In the oral half of the test, the sides converge more or less in a straight line towards the aperture. L = 125-135 µm | H. rosea |
| – | Shell not pink-red. Lips narrow more or less colorless, outline more oval | 4 |
| 4 | Shell relatively narrow, mostly irregular, sometimes with a regular pattern mostly colorless, sometimes light yellow or light violet. Covered with various small particles and at the aboral end larger mineral particles. Size 95-100 µm. Size and shape vary. Mostly on Sphagnum mosses. | H. petricola |
| – | Larger than type (125-150 µm). Shell composed of irregular scales. Color when living: bright violet. In lakes (deep water) | H. petricola v. amethysta |
| – | Shell broader, with a regular pattern, usually with some mineral particles or diatoms at the aboral end. Color: yellow-brown. Size about 100 µm. Mostly on Sphagnum mosses. Only species of this genus contain symbiotic algae (zoochlorellae) | H. sphagni – H. picta |
Key after Edward Mitchell, 2003