Water Buffering Rocks/substrate

[kj23502]

I see subsrate mixtures that buffer water to a higher ph and also large rocks such as limestone. My question is, is it possible to have too much of this stuff(rocks and substrate) in the tank? Or does it stop when the water gets to a certain level?
Thanks

 

[darrel69]

I dont think you can have too much. Im not sure, but i think it only starts to harden your water if your ph drops below 7.8

 

[dthoffsett]

I don't think you have to worry about too much buffering, limestone and aragonite type substrates leach out their minerals at a fairly slow rate, and if you are doing your weekly water changes (which are necessary with mbuna) you'll be regularly adding fresh water which will dilute your tank water.