Why is this a bad combination? The only problem would be the convicts as stated. The only way I would do the cons is if you get same sex across the board. Something like a 135 would be slightly crowded if you added ANY deco, which you hopefully should. A 180 as already said would be a perfect long term tank for this combination. If you wanted to substitute the cons, good replacemants would be firemouth, port acara, festivum, (the latter will depend on availability) as well as many others that stay in that size range. You could even get something a little bigger than that if you go with a 180. Also, if you do the pictus, I'd do a small group of 3-5, as they are a schooling cat that are FAR more interesting when kept this way.