I am sure you are not an idiot… Though, I have been wrong before…
I think you may be dealing with a situation that is out of the ordinary.
If you would like help, try to keep this post self-contained so we have the information here. Nothing introduced as a surprise from another thread or site.
From the beginning, tell us about your tank, particular attention to information about the tank, size lighting, and critters, plants, how long, so no.
Tell us about water parameters, tap and tank, try to avoid slang or acronyms, how you know what you know, if you do not know something that is okay, say so.
Yikes, here it is; hopefully no acronyms (I am always trying to keep posts short -
Innovative Marine SR80 (80 gallon) 48x18x16 has 2- 476gph pumps with overflow filter, good surface movement, but not filtering at bottom of tank. I added 2 airstones on timers and small water movement pump near bottom.
Eco-xotic LED light, eco-complete with Carib-sea sand foreground, malaysian driftwood-not too heavy with open areas, 3 small slate rocks (did not bubble with vinegar) low tech (Excel), Seachem ferts, mod to high number of plants which are all doing great, UV.
I just tested filtered water-at 9dGH, 4-5dKH, 8.8 pH. These have changed from when I started; hmm, I am going to change out the filters even though they are only 3 months old. Our city water is notorious for not being the best for fish according to my LFS. Tank is 10dGH, 4dKH, 7.4 pH in am and now 7.8 in pm (started using more RO water). Using new API test kit. Tested oxygen a week ago and got a reading of 6ppm at night and 8ppm in am. 0 ammonia, 0 nitrite, 0 nitrate, temp at 76.4.
Started fishless cycle on 9-16. Currently have 5 corys, 2 harlequin raspbora, 1 furcata rainbow, 7 rummynose. Helpful?! I have posted on other threads and you have responded (thank you)! Just want to be sure I am not missing anything now as I may have it under better control by using more RO water, I think!!!! I am using an aquarium maintenance app so I keep pretty careful notes. The test results can be tricky to read however! PS - I do not let water sit before testing pH; should I?