Just trying to get a handle on what to look for or test for in order to see if my co2 is too much. I know we can look for fish gasping at the surface. I have not seen this, but my SAE's seem to be hanging out on the bottom a bit more then they used to. But my tetras and killis are hanging around like normal. Is this our only real indicator of excess or too little co2? Can we also check ph and make any assumptions? My GH outta the tap is about 5 and i put a tsp of gh booster at water change. Does any of this data help me?