The first thing to ask is what is the gravel substrate in the tank, the next is to ask the tank decor (rock, ornaments etc). Something is obviously buffering the pH and hardness in the tank to remain that high. Calcium and magnesium carbonate are the 2 primary contenders, so any coral, limestone, etc is immediately out, as are many other rocks.

next question is, what is the pH and hardness of the water going into the tank.

Be aware that African Cichlids do well in alkaline water, with a high pH, but some of them are very aggressive (well, pretty much all except the leptosoma are aggressive.) If you want something a little more calm than they are, Guppies, Swordtails, Mollies, Platies and other live bearers do very well in a high pH and hardness. Just make sure there is plenty of Java Moss for the babies to hide in.