OK, 1st off, it's not my fault. The situation was dropped on me- the co worker "taking care" of the tank got fired.
55 gallon, nice set up, couple of plants... OVER STOCKED. (I'm working on this part and the boss)
I tested the water before I started the water change (you know, to know how much to take out). I was shocked to see our nitrates off the chart.
Makes sense when you consider the over stocked issue and that he wasn't on the ball with the tank.
So I did a 30% water change because my back is just killing me after that much lifting of 8 gallon buckets. Two days later I went back and tested again, we're still stupid high (which I expected since it was stupid high before). We went from I'd guess 160 (hard to tell that far red) to a probably 110. Still lethal. Fish don't seem too stressed out about it, just stressed about people messing in the tank. The first water change had nasty amounts of poo from the gravel vacing, second significantly less than I expected considering the still high level of nitrates. So I think the gravel is pretty clean all things considered.
Here's my question... How many times can I do a 30% water change every other day until I do harm to the bacteria and screw it all up? I know I have to get the nitrates down ASAP, but don't want to mess it up even worse than what's going on now. I've just never had to reduce levels this much before, I always stay on top of it at home.
P.S. as for the over stocking, I know it's an issue and if it was my tank I'd take care of it right away, but office politics is not letting this be an option. I realize that this (and the neglect) is the reason for the sky high nitrates but hands are $^#%@ tied about it right now. Got to make the best of the situation.