the 16 gallon is nice. I have one set up at my inlaws that I'm going to take down soon but it gets small pretty fast. 4-t5s prob wont fit as the usable space is very narrow. LEDs will be perfect. I have an ecoxotic 24" Panorama on top and it can handle zoos and leathers duncans and an RBTA no problem. I really like the 24 gal though.