So for ammonia and ammonium tests I use the seachem free and total. I just got back from the cottage and of course one of the first things I want to do is check my tanks and make sure they are perfect. My fiance did an awesome job taking care of our tanks over the weekend. Last night in our 50 gallon it was tested at 0.02 (parts per trillion) well my fiance and I set up our test like we always do, the 15 gallon is cycled no ammonia very low nitrates no nitrites or ammonium. But .....just then.....the look on my fiances face was utter horror when he looked at the free ammonia test FREAKING 6.0PPM I couldnt believe it we looked at our tank the fish arent gasping at the top or plants are ALL alive the freaking hornwort has grown like crazy so we test again with the same results. So we get our other seachem box to test and omg we left it for 30 minutes and watched as every second went by. Wr had a false high positive. It's only at 0.02ppt I THOUGHT I WAS GOING TO HAVE A HEART ATTACK I didnt know what I was going to do all the stores are closed today for things I'd need. But it's fine.....but a warning for all you beginners out there FALSE POSITIVES ARE THE DEVIL. be careful when testing make sure you have a in date test kit and one that isnt over used or you WILL get false positives when you've got a large amount of ammonium and a very small amount of ammonia. Make sure you know the difference. The api fresh water master kit doesnt differentiate between ammonia and ammonium. Make sure you have something that tests the difference save your self the tears and sense of failure when you're not failing at all!