No, your ammonia increased due to an increase in ammonia creating critters. Your bacterial community will grow until one of two things happen. There is not enough food(TAN, NO2), or the surface area for them to grow on becomes limiting.
Add the tilapia.
I would also keep an eye on the pH. It is fine for now, but a little low for the lack of nitrification already in progress. Nitrification consumes alkalinity, and produces carbonic acid.
There isn't enough nitrification going on... under the current load.... to make any significant movement of pH at the moment..
Get some crushed oyster shells or limestone chips that are usually sold at farm or feed stores to use for chicken grit. Put them in a mesh bag or stocking and tie it up and hang it in the fish tank to keep the pH from dropping too low.