i would treat smaragdina as you would splendens. do the fish a favour and let him be "king of the tank", he will thank you for it.
10 gallon would be fine, if it was my tank i would heavily plant it with the floating variety, and age the water with IAL. the tank would be kept at half-full water level as well.
also, i would have a large tall jar with same aged water ready for when i transfer the male out of his "environment tank" and into the display jar. it is important to give him a regular flare time with other males etc. and jarring him makes it easier. it is recommended that you either make or invest in a "krabouy" or scoop for transfering the fish. get one where the pocket is water proof, this way the fish will be moved in his own water and it will be less stressful for him.