Any suggestions?

[Bootler]

i have been in the fish keeping hobby for over a year now and i have learned how to take care of my fish. my first batch of fish i owned died after 3 months. i really learned from my mistakes. i bought 2 tanks after my first batch died and i stocked all my tanks up with different types of fish. i bought a 75 for my little reticulated ray, and a 29 gal as a temporary home for my piranhas. in the 35 i kept it a community tank to keep my mom happy. i love my stingray and my black ghost knife. they have been very healthy and active for the past 7-8 months. i am rather bored of my community tank filled with 2 angels, 2 powder blue gouramis, a molly and a guppy. i have been thinking and thought to try to get new stock. i am considering to make my 35 gal a smaller salt water tank. would this work? what kinds of fish would you suggest to put in this aquarium? also for my 29 gal. i have 3 red bellies at around 4 inches each. they will out grow my tank shortly. what would you guys suggest to put in that 29 gallon? i want a unique type of fish. i'm not into chiclids very much. i was thinking maybe a hujeta gar. would this work? thanks