Matching Tank Parameter

[wolfwolf]

I have a mbuna cichlid tank setup. I added cichlid salt and a pH booster. My tank parameter are ph8.0 kH 5.0 and gH 25. I got my buckets ready to do a water change. I added a proportionate amount of material to my water buckets. I got pH8.0 kH 5.0 and gH 10. Why is my gH so low in the water change buckets? Can I still do a water change?

I have marine sand in my aquarium along with lots of rocks (being mbuna). Would it increase my gH by that much?

The rocks are slate, tufa, and anothe rock that I do not know but it was identified by the LFS as inert.

Help...

 

[OldMan47]

Marine sand should be driving the KH up along with the GH. The calcium carbonate that dissolves from it will help keep the water hard and increase alkalinity. The calcium of that compound goes to GH while the carbonate moves up KH.

 

[wolfwolf]

So can I do a water change with a tank at gH 24 and the water to be added at gH 10? Would a 20% water change hurt the fish?