You could keep Duboisi with pretty much any other variant of tropheus as long as it isn't another Duboisi type without fear of hybridization. So with that in mind your possibilities for another variant are limited only by what you can get. You could easily house two colonies of 25-30 fish in that tank for a total of 50-60 tropheus.
That tank measures 107"L x 16.5"W x 30"H for 230 gallons. That will make for a nice tropheus tank. The only cichlids that would really use a tank that tall are Discus and Angelfish. But with that many fish in the tank I don't think you have to worry about it.
If you haven't already done so you can look at the
tropheus profile section for a better idea of what second species to keep. Any of the reds or rainbows would look nice as well as Ikola's.
Keep us posted on what you decide. Pictures are a MUST! :thumb:
What are you going to have for filtration?