I wouldn't add elassoma, they'll very quickly get outcompeted by everything you're planning on putting in there. They are very timid and finicky with food, often needing live foods, which ofc being outside would help with, but their params are also the opposite of everything else you plan on getting.
Fishbase gets it's lengths from max sizes RECORDED in the wild. Prey fish like these are seldom able to reach the sizes they do in captivity, and even less likely for these fish to be measured and put into a scientific database rather than be eaten when caught. 6" nanolutea was hearsay from Kevin at TUIC. I did have a 5" male though. As for myrnae:
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(Duanes can verify the 7" with his past male, if I pressed this guy up to the glass he'd probably give a more accurate measurement, but alas I cannot because while it is in my house, it is not my fish.)
I have kept and bred every species of amatitlania and cryptoheros except for altoflava and spilurus. Nanos need mature tanks with a lot for the fry to graze on. In spite of the fact that their stomach contents revealed something to the effect of 70% plant matter, my pair really liked protein, whether that came in the form of crickets, mealworms, or livebearer fry. Ironically again, myrnae have more of a varied diet, yet in my time keeping them they haven't gone after:
- inch long rainbows
- loaches
- siamese algae eaters
- tetras
- plecos
- mollies/swordtails
Another reason I'd say the nanos wouldn't make good pond fish is the fact that you're inevitably going to be catching them out and moving them inside. This poses two problems, one being that the stress of the move may compromise their immune systems, and the other being that you will need an equally mature setup to transfer the fry to. I know that sounds over the top, but nearly every time I've moved fry they have died off. The only occasions where fry survived (three individuals out of 400 fry) were being moved to densely planted setups or tanks that had been up for decades. There they went on to grow about an inch over the course of a year. In the span of the time you will have them outside, they will likely not attain enough growth to handle a move once you pull them in for the fall. Getting breeding individuals is also a bit of a hassle, as they only breed at about 2" or 2 years of age. Most online are sold at about half that size.
Amatitlania is actually split into two subgenera, being Amatitlania (kanna and nigrofasciata) and Bussingius (myrnae, septemfasciata, nano, alto, sajica). The bussingius species are for the most part very different from your traditional convicts.
Sajica is actually the closest to the "convict" lineage, but is still a weird one, as they regularly hit 6-10", and cannot handle the cold. Mine would go into shock when I tried to do cold waterchanges like I would on my other amatitlania. Took me too many cold waterchanges to realize there wasn't some weird disease running through my group of growouts, putting them through unnecessary suffering, only to realize that dunking them in water of a more comfortable temp calmed them down immediately. Their eggs are red, and they do not like company when spawning.
Nanolutea I've already talked about enough, altoflava-- not much is known about them but I have a few trade secrets I'm holding onto for myself.
Septemfasciata is probably the closest to actual convicts in terms of behavior. These also get big, as I have a 6.5" male in my fishroom right now, and have seen 8" males in person. They are extremely prolific and form colonies. These like hot water (I spawn mine around 83F), and will lay around 200-400 eggs every 2-3 weeks. These cannot be kept with smaller fish, as they are the only amatitlania that is known to actively hunt smaller fish. I proved that out the hard way. I refer to these as "convict premium" to my friends. Far more aggressive than trade strain convicts. I am actually keeping my male with a female umbee right now.
Myrnae ime also stay near the bottom a lot more. The nanos would come up to graze on floating plants. My male cleaned all of the duckweed out of his tank, and moved on to the salvinia, before stopping on the frogbit, which he of course, could not eat. My female died at about 6 years of age, so I rehomed the male.