A tank that makes them feel secure but doesn't let them hide out of sight all the time tends to acclimate them faster. Looks like no background on the tank? So, not telling you what to do, but if it was me I'd add sand and a background (or paint a background), remove the tall rocks and replace them with low lying rocks-- or lay some of yours on their side if it accomplishes the same thing. Making the tank feel more enclosed (background and sand) and providing some structure should help them settle in and feel comfortable faster than their current situation.
What type of African cichlids do you have? GTs will actually work pretty well with some of them, not such a good idea with some others.