last i heard, cichlids are happy with a PH around 8.
if your insistant on changing your water's PH, do it slowly
if you have a pleco, what kind ?
some pleco's prefer wood in the tank, ... actually they eat the wood - not all pleco's mind you.
wood will also release tanin (tanic acid) into the water column and will try to lower the PH
-in addition to turning your water a watered down tea color
don't use any wood, there's safe wood, and unsafe wood
unsafe wood is loaded it's it's own preservative to ensure it's own survival from disease and infection of the tree, ... some of these trees the toxin is ...
to reduce this toxin, boil the wood, drain, and boil again, one species of tree the first water you get from this process can be used as an effective poison for killing in even small amounts, ... and other species of trees it's present just no where near those concentrations, ... not the stuff you want leeching into your tank.
so find wood that is safe, ... or find aged wood that has had this toxin leached out of it by exposure to the elements for an extended period of time, ... just stay away from fresh/live wood.
or you can play it safe and buy something from your LFS.
now the scary part is over
the good part
wood has tanic acid that will lower your tanks PH
wood is good for 'some' pleco's, (what kind of pleco do you have ? is this a concern)
could solve 2 issues in one step.
otherwise, if your tank inhabitants are doing fine, deliberatly changing water parameters is going to be a source of stress instead of helping bring the balance you seek..
other then that, i don't know how quickly the tanic acid in the wood will act, nor do i know how low it will try to drive the PH