Auratus and P. Zebra both get too aggressive to be in a thirty unless they are juviniles- even then the smallest tank size recommended for these larger malawis is 55 gallon due to the nasty temperment. I would not do both in anything smaller than that, unless you want dead fish eventually and extreme water changes to keep good conditions. I started with my psuedotropheus' in a 29, now I have upped it to a fifty five and added a few more in, and its perfect. If you stay with the thirty you can try to exchange them for some rams, shell dwellers or kribs- all are awesome nasty little buggers that do well in a smaller set up.