My buddy lives on the 3rd floor and has a 150g...are your apartments super old or something?
Nope, built about 4 years ago. But they build these apts quick and cheaply. I've got a 75g, 55g, 29g, 24g, several small tanks, and now this half filled 50g in a 1 bedroom apt. I've spaced the tanks out and the 75g, 24g, and this tank are on exterior walls, but still...
Some tangs wont use much of the upper 1/2-1/3 anyways unless you plan on really building up the rockwork...at least when it comes the the julies IME since they mainly stick to the rock. The multis, of course, could care less. Heck, you could always add some riparium plants in baskets attached to the back glass to add more dimension to the tank.
I dont see a whole lot of shells though (although I could be mis-seeing)...how many multis are in the tank total? Make sure you've got 2-3 per fish.
I actually added some riparium plants today. Made my own version of ghetto riparium planters by taking the AC sponges I've been using as prefilters and using them as planters. I figure they're loaded with all sorts of mankiness the plants will like, plus I needed to replace them anyway. I shoved 2 of the plants into the holey rock and 2 I suction cupped to the back. We'll see if it works.
There aren't a lot of shells in there, but my multies are weird. Even in their old tank they didn't use the shells much, they preferred the holey rock. I do plan on getting some more shells when I find some. There are only 4 multies in there right now (the ones that hid when I was catching the colony to take to the auction) and 6 shells. The male won't use the shells at all.