Well my 55 and 10 as of today are officially cycled! They both can consume 3 ppm ammonia in 24hrs and both ammonia and nitrite are back to 0 ppm. I've dropped the temp down to around 77 in both tanks and it will soon be time to head to the LFS for some new fish. But before that I have a concern about the pH in the 55, here goes... Once I started cycling the tanks here is how the pH readings have gone: Date pH Notes 2/19 7.6 Filled with tap water (dechlorinated) and added ammonia to 6 ppm 2/22 7.8 Ammonia was still 6ppm, no more had been added 2/23 7.7 Ammonia was still 6ppm, no more had been added 2/26 6.8 Ammonia starting to fall, down to 3 ppm Later that night ammonia dropped to 0, brought back up to 3 ppm 2/27 6.9 2/28 6.7 3/1 6.0 3/2 6.0 3/2 7.3 After a MWC (~99%) to get my nitrite reading down 3/3 7.2 3/4 7.6 This is when the nitrIte --> nitrAte bacteria started kicking in 3/5 6.2 3/6 6.0 The pH in the 10 gallon pretty much mirrored what the 55 did up until the MWC (on both tanks) of about 99%. Since 3/2 the pH in the 10 has stayed pretty steady at 7.2 as of yesterday. Today is read 7.0 but I did add some driftwood to the tanks last night. I'm pretty confident that the 10 is ready to be stocked after another MWC but the 55 I don't know ??? Anyway to make a long story short, should I be concerned about the pH fluctuation in 55? Or once I drain and refill it in preparation for fish will the pH stabilize?