Gdeboeck,
African cichlids like hard water. Your water is quite hard--215
ppm, or dGH of 12. This is excellent. Is your tap water naturally this hard? If so, excellent. You're in a perrfect
GH condition. ACs generally like a hard, alkaline water with a dGH of 10-15 (some 10-20), and a pH between 7 and 9. 8 is a usual pH for these guys.
As far as I understand it, ACs also like a high carbonate hardness. Many rock sellers online sell "African Cichlid Rocks," limestones (Calcium Carbonate), which will increase pH, dGH and dKH. It looks like you have a moderately high dKH, 7 dKH or 125
ppm. This is fine, though some might say to raise it.
Rocks that are carbonates (i.e. limestone) will certainly increase parameters as I mentioned above. Most aquarium rocks are sold to be neutral, though, and probably won't affect your dGH and dKH too much.
You've gotta get your convention down, though. You seem to be confusing yourself by using both the German hardness system (dGH) and the parts-per-million system. Use one or the other...
Oh, and it's "carbonate" hardness,
btw. Carbon is an element, carbonate is a molecule (anion) which includes carbon.
One question: what are your pHs on the two tanks? The cichlid tank should have a high pH around 8, but your oscar tank should be mildly acidic (pH of 6.5 or so). The oscar is a South American cichlid, and they generally like acidic water, though they can tolerate a pH of up to 8. Consider getting a piece of driftwood. Also, consider getting a larger tank soon. Oscars, when older, need a very large tank. If you keep them in a small tank, you will stunt their growth (but you probably know that).
Lastly, this like will give you an idea of
GH, pH for ACs:
http://www.liveaquaria.com/product/scateg.cfm?siteid=21&pCatId=831
Good luck.
