As you may know I have an 125 gallon Cichlid tank that houses: 2 Oscars, 1 JD, 1 GT and 5 Silver Dollars. For filtration I have 2-Eheim 2075's and 1 Marineland Magnum 350 Pro, which brings my total filtration to 1010 GPH.
Anyways, I did my wc this Monday night and of course turned off all 3 filters off before adding new water, but when I turned back on the filters I forgot to turn one of them back on. I forgot to turn one of my Eheim's on, oops. I just noticed today (3 days later) that there was no water movement from that filters outlet. I knew enough to not just turn the filter on as it would cause huge problems if I were to let all that dead bacteria into the main water column, so instead I did a round of water testing. This is why I LOVE my currently redundant filtration setup, as the 2 other filters covered without any problems or spikes. Just to be sure I tested my water with 2 test kits, my main test kit (API Master Kit) and also with a backup kit (a Tetra master kit). My readings were as follows:
API Kit / Tetra Kit
Ammonia: 0 or barely off 0 PPM / 0 PPM
Nitrite: 0 PPM / 0 PPM
Nitrate: 10 PPM / N/A
So, the moral of the story is that having extra filtartion is never a bad thing and I personally prefer it, it just might save your tank and inhabitants some day. Of course, I took the filter apart and cleaned it like a crazy man and even flushed the hoses for that filter with tank water before restarting it again.