45 gallon to 112 gallon?? How?

Hey Everyone,

I'm thinking about doing a major swap in my fishes homes. Currently I have a 45 tall that's 4-5 months old with 50lb live rock, 50lb live sand, 1 firefish, 1 flame angel, 1 four line wrasse, 2 clowns, 1 blue reef chromis, and some mushroom corals. i have a HOB protein skimmer rated for 100 gallons.

I want to move all my saltwater inhabitants to my 112 gallon tall African cichlid tank. There are only maybe 3 cichlids that i actually want to keep, transfering them to the 45 after everything is done. The cichlid tank is setup with a 15 gallon sump, which I'm not sure if it would be large enough for saltwater... maybe if i have to use the 45?? (get rid of all the cichlids ) or i also have a spare 20 long, i could maybe somehow connect the current 15g sump to the 20g long (like different chambers). Would i be able to use my current HOB skimmer in one of the sump tanks? or would i need a different type/size? the 112 is acrylic so it has a acrylic bracing top, the 15g sump is also acrylic (flimsy too).

And the major question is how do i pull off this switch? All I have is that spare 20 long, a 10 gallon, and three 18 gallon tubs...
What would be the best way to cycle/seed the new saltwater tank and where could i keep all my fish, sand, rock, coral during the process?

Heres some pics:
Current cichlid setup


Current Saltwater setup


Possible New setup?



THANK YOU!

 

Rubber made tubs. The bacteria on the rock work and sand, not in the water column. Shouldn't have to worry about that.

There is no "sump requirement" so you can go as little or as big as you want, just make sure you can fit what you need into that sump.