When cycling a tank you need to monitor ammonia, nitrite and nitrate. But yes a test kit is best for this

@@EnglishAquarist thanks!!

How did you achieve 0ppm ammonia

@@deathscythe3124 the tank has matured and has beneficial bacteria "Nitrosomonas and Nitrosococcus" which convert the ammonia. Products like API quick start can help this process.

If you push down while twisting, it should open easier.

You just need to make your ammonia is at 0ppm. You can do this by adding cycled media from another mature aquarium or using bottled beneficial bacteria. Then your aquarium will convert ammonia to nitrite then to nitrate which can be removed by plants or water changes.

@@EnglishAquarist my aquarium is so annoying. The ammonia and nitrate levels are so unstable! The nitrates go super high (but my fish look healthy) and my ammonia was at .50ppm today! I’m basically doing water changes daily to get rid of it. Any tips on keeping the ammonia low? I do already have a lot of live plants.

Have you checked the water that you are adding is ammonia free? When you use a declorinator to remove the chlorine and chloramine as chloramine is broken down, it produces ammonia. Does the product you're using detoxify it?

@@EnglishAquarist I use prime and add it to the entire tank once I have added the tap water in

@user-ds2lt5fi7c when you use prime it toxifies the chlorine and then breaks down the chloramine and the left over is ammonia. If the ammonia isn't converted by the biofilter it will cause an ammonia spike. You might be best buying some beneficial bacteria that will break down the ammonia into nitrite then into nitrate.