For a long long time I used only store bought spring water for my tanks. Its a little pricey but the parameters on it are primo right out of the bottle. Low ph, fair kh, and no chlorine or chloramines or any other nasty things. But recently ive started using tap water for my water changes. My tap water params are almost exactly like yours. Upper 7's on Ph, Kh and Gh off the charts. I use Prime to condition the tap water before I add it. My fish seem to be doing just fine, and no effect on colors. I started using tap water as a means of conditioning them for their new home. Recently acquired a 350g and its filled with conditioned tap water. So the water changes with tap water are in a sense a "drip" method of acclimating them to the new tank. After another 2-3 weeks the big tank will be cycled, and my fish will be adjusted to the new parameters of the tap water.
One advantage to low ph is ammonia toxicity. I read somewhere recently that ammonia actually turns into ammonium in ph lower than 7, and ammonium isnt as toxic as ammonia which occurs in ph higher than 7. Being that Cichla are not very tolerant to ammonia, lower ph would be beneficial in that sense. On a side note, I have 3 XXL pieces of driftwood in the new tank, and my ph in the tank is no lower than it is right out of the tap. Its the same. The wood has released lots of tannins, my water looks like light tea at the moment, but ph is still exactly where it was before it went in the tank...
