I'm not sure what happened. A guess is that the water in the tap has decreased in PH. That is a reasonable guess, as we've had a lot of rain in the late summer. And much rain often means lower PH in the tap. I haven't tested the water for a long, long time, as it rarely changes. Besides, my PH pen was out of battery, and I threw away my test set a few months ago, as it was out of date. I didn't buy a new one, as I had that PH pen. Because the tap water usually has a PH too high, I have to lower the PH before pumping it into the tank. I know exactly how much oak bark extract to use. But if the tap water has changed, that won't turn out right. Besides, one of the cory species there (there are three groups of cories there) is a species that prefer a very low PH, but this was too much (or rather too little) for even them. But as they want low PH, you can't see them change behaviour so much as you would expect. The other cories has stopped spawning, but I thought it was the summer (many cories stop spawning in the summer).
But this can only be half the explaination. The other tanks I pump water into from the same water storage, has too low PH too, but nothing like this tank (5,8 in the tank closest to it). The low PH tank has a larger wooden root, but I've had it for so long so it shouldn't lower the PH much anymore.
I did read something today though, that can be some of the explaination. Apparently it's more difficult to keep a stable PH in a heavily stacked tank. That was new information for me. And this tank is stacked to the limit. One of the cory groups is supposed to move into another tank, but that tank is currently occupied by my GSP, and the GSP is waiting for me to set up the marine tank I've planned, which of course I don't have money for buying LR for the moment. Besides that tank is now occupied with two groups of cories, which is to be moved to a tank that is now occupied by a lot of suckermouth catfishes and a group of cories, which are supposed to move into a bigger tank that is now standing empty on my kitchen floor (and has stood there for a year
). So I need to do a lot of moving fishes around before I can give my c. trilineatus a tank all by themselves.
Well, maybe this PH problem is what I need to make me start all this moving around.
But one thing is for sure: I will start monitoring the PH in this tank again! Poor beautiful, little cories! And they amaze me with their ability to survive!
It's amazing that the cories still are doing so well. Be sure that I will slowly bringing the PH up in that tank...