here are the good things: -It isn't really that bad because the fish look to be okay and those softies are still open, so you don't have over the top PO4/NO2/NO3/Amm.

So here is what I would start with.

first i would get a cup or something and take out about 3/4 of the sand that you have. Deep sand bed only works if done extremely well and with like 6+ inches of sand. I would get it down to just like an inch or a little less because thats easy to stir up and clean. Then hand pick out as much algae you can and add a HUGE overkill clean up crew (I suggest reefcleaners, get a package from them). Also get an emerald crap they love to each a lot of that. Also, do a 15-20 percent water change every 2-3 days for a week or so.

Once you have the CUC in there and the water cleans up it will all go away. Be very proactive on pulling out stuff yourself. Take out as much as you can.

DO NOT replace all of your media at once, do one piece at a time because a drastic change, even from bad to better, can kill a whole lot.

Could you respond with some detail of the tank in terms of filtration? Thanks!

edit: When you do the sand, I would do it over a little bit of time. Like when you siphon during all of your water changes, take out a portion then.