I have a 30g tank; currently been cycling for 2 weeks. It has live rock and live sand in it.
Last night, I cleaned my filter and added 1.5g of freshwater to top off the tank from evaporation.
About two hours later, I did a water test and found the pH had dropped to 7.7 every few hrs I tested the water... and it slowly went down to 7.2. It seems to be holding at that pH.
Im going for a reef tank so I've been told that 8.1-8.4 is nominal for pH.
Is the drop in pH to be expected when adding freshwater to top off the tank?
Will it rise back to its original 7.9?
And if it is to be expected then will a drop like that hurt the corals, inverts., and fish that I will eventually have?
I don't use tap water; instead i use RO jugged water which has a pH of 7.1.
My KH is 300ppm. I dont have a GH test.