Water change not effecting nitrite level

Glad to hear things improved.
 
your nitrtes are rising because youve fully stocked the tank already. having two common plecos is way to much for a 55 gallon tank, for they produce so mcuh waste. that could be the underlying problem here.

Size really does matter!!! :D Since they just came from the LFS, there is no way they are the contributing factor right now (or for this year).

The tank is limited to "garbage in; garbage out". The nitrogen cycle is limited to how much organics (food or dead fish) is added to the system. If the amount of food added today is the same as what is added next year, the nitrogen cycle will have the same bio-load even though the fish are larger.
 
prime... ...the chlorine basically just off gasses..

Just a little trivial info: the end product of the chlorine is salt. Sodium Thiosulfate is the most common dechlor chemical. The sodium combines with the chlorine (in the form of Hypochlorous Acid) to form Sodium Chloride (salt). The amount of salt produced is very minimal. Any salt is good salt :D
 
I am surprised no one mentioned to get some old filter material from the LFS to seed the new filter. The gunk from an established filter is the fastest way to cycle a new filter.
 
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