The speed of a cycle

Had a fish die in my 55G on Tuesday, Didn't think much of it and since it was the end of the day I just netted it out and went to the faculty meeting. Next day I was SLAMMED with watching not only my class, but another one that was shoved into my room. Needless to say, I didn't have time to do more than toss some food in.

Yesterday I came in to find 3 of my smallmouth dead. Fished them out, checked levels. Major Ammonia spike was the culprit. Since I was stuck with one of my classes for 3hours straight (State's EOCs being taken for other core courses) - I lectured for the first two, then we reviewed the Nitrogen cycle and did a 50% water change as a class. This brought the NH4 down from 8ppm to 4ppm. Afterschool (7 hours later) I did another 50% water change, which brought NH4 down to 1.0ppm.

This morning I did a check and NH4 was now down to 0.25ppm. I pulled the in-tank filter to lightly rinse it, found a dead small sunfish - netting it out. Rinsed filter, set it on high - and then checked Nitrites. They were at 5.0ppm. Figured I'd do another large water change afterschool if needed. Checked the nitrite levels during lunch (4 hours later) and they are down to 0.25ppm already! Amazing how fast those bacteria work in an established tank!

Nitrates are going up slightly, but the duckweed/pond lilly/water iris are doing their part. Tank is a little lighter in fish population now - but at least my 3rd period students got a real hands-on experience in dealing with chemistry imbalance in an aquarium.