The friend's tank has only a single angel fish and a single pleco in it. The hornwort came from my tank which had only cories in it as well as a musk turtle..
However 6 melanotaenia splendida were added to the tank around the same time. I cannot remember if i transferred the hornwort befre or after I added them, but i did wash the hornwort before I put it in my tank. they were all about an inch long and too small to breed I thought, but I could be wrong. If it is anything that came in on the hornwort then it would be M. splendida, but my friend just told me that she only had the plants she gave me for a week before giving me the cuttings so it could have been anything in the LFS she got the plants from.
all the fish in my big tank died from some sort of black fungus/algae/something because my dad overfed them while i was out of town so maybe this is the sole remaining survivor of the tank?