I am forced to question the reliability and accuracy of the test materials that you are using. You previously stated that you obtained a mid-day pH reading of 9.0 and now you are saying that the early AM pH reading is 5.0. That is a 4.0 point swing in 4 - 5 hours. This abrupt and enormous change in pH would result in, at the least, definite signs of stress in your fish and most probably occurrences of mortality. Since this is evidently not the case, based on one of your earlier posts, the test results must be inaccurate. Before you pursue any remedial action you must ascertain EXACT and ACCURATE parameter levels.
