Freaking nitrates

I totally agree with much of what has been said about your sand bed. Literally last week at work we had to convert a clients sand bed. The best way to do it is also a huge PITA. We bring a rubbermade 55 gallon barrel. Fill it with as much aquarium water as you can, THEN add liverock and livestock. Add small powerhead next to heater as well as an airstone away from the powerhead.

Then you could leave the barrel the way it is for some time. Take your time using whatever method works for you. I would not go at your tank with the assumption that the new sand will settle to the bottom. Your sand looks a lot like caribsea seafloor special grade. You want some kind of oolitic aragonite or sugar grain sized aragonite.

I would remove all of the sand and replace with 1.5-2" of dry oolitic. Its less than $1/lb. Seed it with sand from a fellow members astablished tank. Allow the dust to settle in your 55 aquarium after it has been completely filled with salt water. Then do a massive water change introducing your old tank water back into your aquarium with the livestock as well. This will be some work but will work. And will give you far fewer headaches in the future.

Also, how often are you not just emptying but cleaning your skimmer head?

And try not to get overwhelmed with this task. Once its done, its done forever right? haha

Oh! And when you put your liverock back in, push it down to the glass. The rock will essentially draw more water through your sand bed/biofilter this way in addition to be being more stable.

There are a few columns in the craigslist adds. A small column type aquarium would make a really nice fuge on the left there. You could put it low and box it in. Or put it on the stand you are likely to get with it and then put your gear underneath. Both would work. Seeing as how you will want to run the light at night time with a reverse night day cycle or 24hr cycle, you may want to keep the light in a cabinet if it will be an issue at night. A good 3 inch oolitic sand bed, topped with 1/4" or less of the special grade sand u have already, and then a sprinkle of large crushed coral, and you will have niice microfauna factory down there You can have the fuge drilled real cheap now too. Or diy!

Is that by chance a power strip or two lying on the floor behind the tank?

I don't know what all that tank is on the right. If you are handy, that stand could be modified to accommodate a 15 or a 20-long pretty easily, maybe even without moving the tank. If you are really handy, you could build a sump/refugium to your own specs with glass, or acrylic, or even plywood.

What Sokretys suggests would put more water in your system, which is never a bad thing.