Well, if there's any
presence of ammo & nitrites, the tank isn't cycled yet, or something happened that caused a mini-cycle......
How old is the tank?
What kind of filtration is he using?
What is the livestock?
How often & how much does he feed?
What kind of substrate?
Does the substrate occasionally get vacuumed with water changes?
If it is an established tank, I'm going to take a very wild
stab in the dark and guess it's an overstocked & overfed tank with a shallow sandbed that hasn't been vacuumed in a while, and a canister (or HOB
) filter that is way overdue for a cleaning...... Any of these situations alone will cause higher nitrates, but all of them together will create an out of control freight train.