loki, setting up your tank two weeks before you bought your axie, with water ager and filter running, doesn't mean it's cycled. It wouldn't have started cycling until you added a source of ammonia, ie when you bought your axie and added to the tank and started feeding it so it excretes. Leftover food, regurgitated food or poo/waste are what starts the cycle process in your tank.
Otherwise poor water quality can harm your axie, ie: one symptom can be short gills/gill filaments burning if tank is uncycled and ammonia toxins build up where there are no frequent partial waterchanges.
My advice is to test your tankwater as soon as you can, and if needbe (ammonia or nitrite levels ABOVE 0), then do a 20-30% waterchange. While your tank is cycling, you need to have your tankwater tested every couple of days at least (not weekly). Weekly waterchanges in an cycling tank isn't good for your axie as it won't keep the toxins down.
Another big no no that people tend to do is go the other end of the scale and empty over 50%, 75% or the whole tankwater and start again. This can also cause problems, will cause your tank to start the cycle again.
You can remove your gravel completely and have it bare until you're ready to add sand if you wish.