I'd start with an ATO
Your water line looks pretty low. The salinity must be up and down. Stability is key. Then I would work on the algae problem. Test test test. Next I would look at different lighting that aluminates the whole tank and is rated for corals. Not sure what you have now. That's a good start
Testing would be great, to know what your parameters are at. There are a decent number of fish in your picture, do you have enough rock to maintain bacteria populations for bioload filtration?
I'd start with an ATO
Your water line looks pretty low. The salinity must be up and down. Stability is key. Then I would work on the algae problem. Test test test. Next I would look at different lighting that aluminates the whole tank and is rated for corals. Not sure what you have now. That's a good start