Originally Posted by funkman262
Based on the info that Aurie provided, it sounds like the tank was just set up so it's unlikely that the water chemistry is already being altered by biological activity. The other tank that was established and did not contain driftwood had a pH slightly higher than the tap, not lower.
True, but I think there is more going on here.
Back in post #1, a pH of 6.4 for the tap and the tank is mentioned. Now the tap is higher. Assuming testing is being done correctly, there may be variation in the tap pH.
Also, I have found in my 7 tanks that the pH can be different, even though I carry out comparable maintenance in all of them. The plant and fish load impacts, as may the substrate (if it is different).
My 70g was running for 2 years with Flourite substrate, and the pH remained around 7 to 7.2. About a month ago I tore it down and replaced the Flourite with play sand. With tap water at 7 to 7.2, this tank after just one week was reading 6.8, and after 3 weeks is now reading 6.4 to 6.6. It has a fair amount of wood, all of which was in the old setup.
My 33g is loaded with wood (see photo attached). But the pH is stable around 6.4 to 6.6, and this tank has been running like this for more than 2 years now. Also play sand substrate.