I need some help getting back in the game

I have recently came back to the hobby from simply just keeping my tank alive. I do my water changes and feed my only fish. Green algae has been a problem but not a total take over.

So now with the new found interest I've found to get things back in order, I kept seeing GFO this, GFO that. Then after some search button clicks I found out what GFO is.....now my question is how to use it with mechanical filters? I have several Eheim canisters not being used and a couple of smaller compressed canisters I could work with. I have always used carbon and phosban with success but this seems much simpler.

I know I need to get my phosphates under control. I had planned on doing it my old fashion way but this seems new and interesting to bind the phos.

Topics like this and vodka dosing have lots and lots of opinionated threads that do not lead to a definite proven yes or no answers. So I would like some responses that are more geared towards proven results rather than simply opinions if possible.

Thanks in advance.

Tank size is 70gal bow

about 70lbs to 80-lbs of live rock

about a 2.5 inch sandbed

I would get a media reactor and a small adjustable pump I would not use canister as a first part. Do you have a skimmer?