right now for me its green terror vs jack dempsey and maybe a salvini. also could i put a very large(like 8 inches) common goldfish in there? stupid question probably.
Salvini and JD would be best for this 55g, because they smaller then a GT. I would get a salvini, because they are much nicer looking then the other 2 IMO. I would't add gold fish because they are cold water fish and create a lot of waste.
If you go with GT or Lyonsi, I'd recommend a female. Males get too big to be comfortable in a 55g long term imo. I agree with the dwarf pike suggestion. My sveni is very personable and very predatory. Salvini are gorgeous but have no personality ime.
i say predatory because i would like a fish that would eat anything from the occasional fish to what ever else. i guess kinda omnivores. duh why didnt i think of that before why does mfk have this?