A.viejita vs. mcmasteri

[Fredrik Johannes Borch <fredrikb@stud.nfh.uit.no>]

In my literature I have not been able to find a key on how to tell these two
species apart. Could anyone give me some hints?

I have what I believe to be a group of _A. viejita_  in a 250 liter tank.
They will often spawn after a slight drop in temperature. Has anyone else
had the same experience? 

Contrary to what many breeders do, I do not breed my fish in ultra-clean
bare bottom tanks. I have had best succsess with heavily planted tanks where
I just let the mulm lay on the gravel. That way there will be enough
microorganisms living in the tank to feed the fry through the first critical
days, and if I for some reason do not have the time to feed the fry for a
day, they will have something to chew on. In a community tank this mulm also
serves as protection against predators; if a larger fish aproaches, the fry
just dives into the mulm. 

Some people find my "dirty" tanks unattractive, but I feel it is more
natural. And natural is what I want it to be...

Any opinions/experiences related to this?