My ph tests 7.6 when the light and co2 first comes on after it has been off all night, and when the co2 has been on for several hours it drops to 6.8. My kh is 80ppm so my ph needs to be in the 6.6 or 6.8 range for my plants but is this ph swing harmful to the fish and shrimp? Equipment is listed below in signature. I have some surface agitation with spray bar but water does not break. I'm using an external co2 reactor plumbed on the outlet of my filter.