Hujeta gars might be a possibility if you go for a 55. I've never personally kept them but they look interesting.
Some of the smaller snakehead species might also be an option, are they legal where you are?
As for pikes, it really depends on which species you go for. my C.Lucius is very active!
Snakehead are illegal in the states .
Ill look into c.lucius and a few other species
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