I've had the substrate for about 2 and a half months. It could be reaching the end of its lifetime. I don't think
have any carbonates in here. I have only been using RO water (remineralized back to 6-7 gH).
However, I've found that I might actually have a different problem. Once again I tested today, to find it's shot back up to 7.6+. However, the shrimp were fine; they seem happy as could be. I didn't think such a wild swing would have them looking this good. I tried to think of any other reason, and I took another sample--this time instead of from the surface, I took it from a few inches down. Lo and behold, I've got my nice 6.6 back.
These were about a minute apart (the left being the first).
So now I think that I have a issue with some kind of film at the top of my tank I can't really see, instead of a pH swinging issue. Would there be any other explanation for only the surface of my water reading that high? Or should I never be taking a sample from the surface of my water?
pH should go up, as any dissolved CO2 out gasses into the air.
Would it keep rising after two days or so? I thought that would give it enough time but I might be wrong about that.