JOKERS 29Gallon Biocube

[JOKERacing]

Hi everyone. I am new to the aquatic world. We just recently purchased a biocube and have got it setup for saltwater fish.

I have a few questions and any suggestions to a newbie would be greatly appreciated.

My setup is all stock with what came in the box. I have not removed the bio balls and i am running the stock filter.

My salinity is at 102.6
i have live sand and about 20lbs of live rock.
I also have a heater and its set to 79 degrees.

Do i have to change the water every week even though all I have is the live rock in there?

When would it be safe to put in some bottom feeders and then fish

thank you for any help or suggestions