I got a tank with 8 H tamasopoensis, 6 H labridens 'white' Xiphophorus montezumae and Poecilia mexicana, all from the Rio Tamasopoensis. The tank measures 181 * 60 * 60 cm, which is quite close to 6 * 2* 2 feet
it is decorated with rocks and a bit of wood. I do not have any plants in it
Unfortunately, the tamasopoensis (8) are all male, so perhaps my experiences are somewhat biased. However, I think the tamasopoensis (@ 8 cm a bit smaller than the labridens males @ 10 cm, both bodylength) will not be able to withstand the labridens. I should, however remouve some of the labridens, but they are very, very quick. Therefore, this is not easily done
Fry from the lifebearers normally gets eaten. Once I wanted to remove a school of H labridens fry @ 1 cm, but I found only X montzumae in the net, which were very welcome. Later I managed to get the fast labridens out as well.
Some montezumae were returned @ 3 cm, but this was not large enough to prevent eating them
I think my conclusion will be that this tank is too small for this cichlid combination, after all the labridens wil lgrow to 20 cm for the males, and the lifebearers will, I'm afraid, not manage it at all - labridens is too much a predator