tilapia will be tight in a 55g and will destroy everything in the tank. i wouldnt put my shoal of 6" piranhas in with my tilapia. as an example he broke both plastic, live and silk plants, 4 power heads, 3 filters, and recently his first water heater
The butti and esp the Pbass will get rather big for that tank. I predict the eel gets ate first, then the Pbass. My LFS has a butti that has been bought at least six times, fat little bugger.
my buddy 12-13 inches. had him in with a jag festae blue moorii 4 bichirs for about 3 yrs. he was a peaceful butti and just lately started to get a little mean. i gave him to my friend because if he killed my festae i would have thrown that sucker out in the snow.