Just acquired a 30x18x12

What would you do with this tank? I have this one that is empty and also a 30g long. I'm going to build a mudskipper tank and also a Dart tank out of these two. I know most people with mudskipper tanks keep the water level low, well im going to build an above water platform with fake rock walls and have the water level deep for fish. Which tank would you use for which and why. Or if you have any other suggestions i'll be grateful to hear them

Thanks

Sorry it's actually a 30x12x18 =) Would that work for a Skipper setup, with deep water?

Ok, i'm going to setup a skipper/fish and possibly crab tank. Crabs are up in the air, but defiantly skippers and fish. Would you use 36x12x16 or 30x12x18 tank? I want to have a large body of water and I'll be making a fake rock wall/rocks which will be sitting above and below the water making caves and such as well as support for the top. So which tank would you use to do that and should I add crabs.