To drag us kicking and screaming back on topic.. I think your water might be a bit hard and acidic for most plec's. They prefer more buffered water than cichild thrive in. Plus cichild's have been known to pluck a pleco's eyes out if they are super territorial...
What do you want the pleco for, algae cleaning or just for looks? What kinda cichlid do you have? I saw someone recomend a royal (L190), Royals need to have driftwood in their diet. If you add driftwood to the tank it could lower the ph a bit.