Hmm...I always thought not supposed to change water during cycle, but makes sense if ammonia goes way up.
While we are on nitrate, I have found on my tanks that the bigger 210 has less nitrate issues than the 55, I guess cause of the bigger water volume?
I have gone 5 weeks now with no water change on my 210 (FOWLR) and nitrates are 10, I have gone same amount of time on my 55 (FO) and nitrates are 25.
I do have a clean up crew and LR in the 210, maybe thats what it is?