Newbie tank general discussion because I am bored.

I have a tank that is in my care for 1 week. It was a working reef for 8 years before being torn down. From there it was transfered into a bin full of live rock and kept alive for a few months. The fish were sold back to the store. I have found that I have an Aiptasia situation and am looking to nip it in the bud. Per the owners instructions I have a been testing and have: 0 nitrites 0 nitrates 0-0.2 ppm ammonia 0 phosphates 400ppm calcium 3 days in a row My magnesium was a little bit low at 960 but I dosed a little yesterday and am at 1140 today

I have a cleanup crew and added a lawnmower blenny today and will not be adding anything for while.

I do have a little bit of algae but it doesn't seem to be spreading. The coraline on my LR is still there and not decreasing. My biggest issue is that I have some Aiptasia that are slowly spreading. I see a new one everyday and would like to bring the problem to a halt as safely as possible. Any ideas? Will post tank info below.