You could use the 30 gallon as a grow out. I have 3 very small white calvus in a 29. They are doing really well. It will be a long time until they need a larger tank. Comps and cavlus grow very slowly we are talking years before they are full grown.
i forgot to add this but if i grow them out in the 30 all by themselves but when i upgrade them and i put tankmates in will the altolamps be aggressive towards the new cichlids
You might want some dither fish of some kind while growing them out. They are extremely shy when by themselves. I have some Chalinochromis brichardi in with mine and they do really well.