55 gallon stocking

Polypterus seem to have a very wide range of max sizes and growth rates. Even wild caught sens would struggle to reach 15" in a home aquarium unless caught at that size. Any common one in the hobby that's cheap is almost guaranteed to be captive bred and won't exceed 8-10". Even WC ones rarely exceed 12" in most of MFK's experience.

As for the synodontis it will outgrow your tank. They get to 8-10" easily and may get territorial. They also live 10 years easy
 
Also, I have decided against the syno. All these years I was misinformed about its max size
 
Also, I have decided against the syno. All these years I was misinformed about its max size
my eupterus is every bit of 9" not including tail streamer which adds at least another 3 or so lol. Also F1-Fwhatever indicates the generations of offspring based on how close they are to their wildcaught counterparts. F1 being the first set of offspring from wildcaught animals, then the offspring of those would be F2 and so on.
 
I'll readily concede on moder captive bredn p senegalus--my statement was based on fish kept 10-15 years ago, that most likely were wild caught or nearly.
 
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