I agree, 150 is just not enough space for a bass. Certain sunnies, especially bluegill and redear, get tremendous (12-14" and two pounds or more) and can provide the centerpiece you are looking for. Some of the smaller suckers, such as chubsuckers, jumprocks, and hogsuckers, hit about 18-24" and can be good tankmates for sunnies. However, they (and bullheads) are rooters and may disturb (but not actually eat) your rooted plants. The sunnies themselves will also uproot plants when nesting if there are no suitable clear spaces. Free-floating plants like hornwort should be fine; rooted plants can be wired to large pieces of decor or otherwise weighted to prevent them from being constantly uprooted.