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I always kept some Otocinclus and small numbers of small tetras in my tanks and never had any problems. However, if the female gets stressed, remove them.
Despite the relatively large black area on the caudal peduncle of your wild male (which could point towards A. cf. piaroa from the Rio Negro), I think your fish are in fact A. piaroa.
I have no idea why some macmasteri are sold with the addition "Ashaninka" (which according to Google are an indigenous people living in the rainforests of Peru and in the state of Acre in Brazil, i.e. nowhere near the area in Colombia where A. macmasteri are found) but since your "viejita" are...
A. sp. Steel-blue and A. (cf.) taeniata are ruled out because they show a pronounced pattern of vertical bars in the caudal fin. So your fish are either A. sp. Wangenflecken or one of the A. (cf.) resticulosa forms. Because of the lack of any pattern in the caudal, the very short lateral band...
It's for sure an eunotus-subcomplex species. Unfortunately the new photos are quite blurry, but my guess would be either A. cinilabra or the (for me) indistinguishable A. sp. Roter or A. cf. eunotus (Orangeschwanz).
It's either a resticulosa-complex species, e.g. A. sp. Wangenflecken, or A. sp. Steel-blue. In the latter species males develop a pronounced caudal pattern consisting of vertical stripes. So watch out for this feature.