Help! 3D Printing Corals for Aquarium Decorations
First thing to check it's, What printer are you using? is FDM or SLA/SLS? Technology used is the great bottleneck to achieve the results that you want to. 

Also, going cheap in 3D printing it's a way to get bad results. A good setup it's really important to get a great XY and Z resolution. 

FDM it's not able to achieve the same resolution as SLS/SLA has, but it's cheaper.

If you using FDM try reducing wall speed, that will increase the detail level. Using a smaller nozzle and lower layer settings will increase it as well.

EDIT: Also, you need to check in the 3D model how the model is. If the details that you're looking for are not there, there is nothing else to do but start doing it by hand.