Did you say what type of filter you are running?
Sorry I have been reading numerous posts today.
.5 for ammonia is a little high and since you said 40% pwc I am thinking it was nearly double that. It would be best to do an additional 50% pwc to get the number to .25 or below. btw have you tested your tap water to see if it has ammonia in it? Mine does at different times of the year.
Also Prime water conditioner is great since it helps neutralize ammonia to safer compounds in the water and helps promote a good slime coat as well. It is highly concentrated.
As a side note about your filter media, if it is a HOB (hang on the back) filter, and you have media pads do not use plain untreated tap water on them, and don't almost ever change them as that is where the BB (beneficial bacteria) is located.
So do not wash the filter pad in tap water, you can swish and get the gunk out in the old tank water from the pwc several times as you would be doing several buckets or in the outflow if you have a python type changer. For final rinsing I just take treated water and pour a few plastic to go cups worth of water over it.
If you have room in the hob to hold an additional pad by all means add one more in. That will soon double your BB as the BB grow and multiply, then eventually you will have a cycled tank which can handle the fish waste in a normal way reducing the pwc based on filter capacity and stocking levels.
You have few fish in such a big tank but the water can turn toxic even then. Do you have the ability to test for Nitrites or Nitrates also? You will be needing to do lots of pwc while you are cycling the tank, also be checking the water parameters daily and doing the pwc based on your readings. Fish keeping gets easier after the cycle as long as you get healthy fish, don't over feed, and overstock, keep up on pwc and do your research on which fish you select so they will fit the tank, and not bother/eat each other, have special keeping requirements outside the norm for which main fish you are keeping. Normally easy.