@Dan_P wanted to bring you over to this for one single clue sentence in the description: the ammonia rose.
None of this is ammonia- generating activity, it's not stored in a shallow unaged sandbed, no way.
When I mention unknown metabolites, from materials handling and detritus clouding tripping up colorimetric ammonia kits / non digital threads like this are where the patterns come from. Something ammonia- like caused the spike. On a seneye it would have held consistent, and any spike resolved in 5 mins max... then we'd still be searching for the storage zone in the sand somehow.
Instead of forcing the truth to be a location of ammonia, in that hardscape in order to explain this spike above steady state, i refute the test kit fully.
@George03 what was your ammonia levels before the work
What test kit do you have for ammonia
What is the level now, and most importantly (since we already know how long free ammonia floats around unused in a hungry reef tank): how long did that claimed spike hold? Two days, two hours?
*reason for this post: Dan and I chat about cycling activity, this clue above is about a cycled tank becoming weak, seemingly, then rebounding back.
I claim no reef tank ever has a weak ammonia control phase without a clear, standout cause in each description but this is very very common in reefing. These issues lead to cycle problem posts, so I study them when they're mentioned in passing.