If your tank has been up 4 months, I'm guessing you're fine. Test for NO2/3 and see what values you get. If you had ammonia in the tank, your fish would show it.

So I checked my parameters and they are all looking good. No more ammonia according to my API, Seachem and Hagen test. My Nitrites are 0 as well as the Nitrates. My pH was a bit low so I added some buffer to bring it up a .1, might need to check it tomorrow as well.
Ren