not 100% sure to be honest. i use tetra's aqua safe which was recomended to me a while ago which supposedly does not convert
NH3 to nh4.
what part of the filter did you change out? what exactly does yor filter consist of? meaning what media does it use?
most filters use a sponge, bio stone and carbon or some similar variation. if you changed the carbon and sponge you could have screwed things up. i wouldn't personally touch the filter media until the cycle is complete and even then you have to be carefull because alot of the bacteria live in the filter media (including the carbon). if your not careful and throw it away or wash it out wrong you can destroy it upsetting your cycle.
generally when you do filter maintenance (which you generally dont want to do on the day of
water change, except cleaning out debris from the filter tubes) you change your carbon (usually once a month, you dont even need to use it) and lightly rinse out the sponge using only your aquarium water to do so. sometimes i will very lightly rinse the biostone with aquarium water if its excessively dirty.
by using aquarium water you dont kill any of the bacteria. generally its a good habit to do filter maintenance mid week between water changes...not on the same day. your already removing some or alot of good bacteria via water change and gravel vac....leaving it in the filter at this time helps keep a bit of a
buffer from a bacteria crash preventing a mini cycle or in your case allowing your tank to cycle.
if it was my tank i would only be doing the minimal amount of maintenance right now...carefully monitoring your
ammonia,
nitrite and
nitrate twice a day. do small water changes (only as much as you need to ) just to keep water parameters safe so fish dont die. other than that try to leave things alone as much as possible to let the natural cycle play out. it can take a couple months sometimes. my curent tank took almost two months.
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That's great news!