High ammonia levels after water change

Question
Hello!

I have a lovely 20 gallon freshwater tank that's a little over a month old.  It holds 9 cardinal tetras, 2 cory similis, two female dalmation mollies and a bristlenose pleco.  I've been adding the fish a bit at a time and love my community tank.

I've been trying to be very diligent about water changes and testing - I change 25ish% of the water every week (or more frequently) and test it around twice a week to make sure the ph, nitrates, nitrites and ammonia are where they should be.

I performed a 25% water change this morning, and tested the water this evening.  The initial readout was perfect, but after letting the ammonia test sit for several minutes it went between the 1.5 and 3.0 mark!  A few of my fish swim up to the top now and again, but I haven't noticed any of them hanging out up there and their color looks good.  I was very worried about the readout and immediately did another 35ish% water change, added some extra water conditioner (I use tap water since filtered water with my driftwood tends to bring the ph pretty low) and retested.  I had about the same results.

The nitrites are perfect and the ph is in the acceptable range - around 6.5.  The water is super clear after two changes *laugh* and the fish seem to be acting normally - what am I doing wrong?  Should I wait longer to test the water after doing a partial water change, or are my levels really that high?

Answer
I commend you on being a very good fishkeeper. Your fish are lucky to have a caring owner. However, changing the water every week is a bit too frequent. Its good to keep the tank clean but keeping it too clean, I know it sounds weird, can actually hurt your tank and fish. The tank needs to develop its own natural cleaning system. In fact a very mature tank needs nearly no maintainence except the occasional wipe down on the walls and a water change here and there and filter cleaning. You should really only change about 15 % of the water every three to four weeks. I know, its a big difference from what you have been doing but it allows the fish tank to creat a natural environment and this means better, healthier fish and less work for you! As for the results, I would not be too worried about them right now as the water change could have affected the results. Also, if you left the test longer than the instructions, let it sit longer, that can also affect how it reads. If left longer it can give a bad reading. I would just wait alittle and test in two or three days. If the fish start acting odd, get an ammonia down treatment to quickly lower the ammonia. Otherwise, if the fish are acting normal, leave the tank alone and do not add anything for two or three days. If after the two or three days the ammonia still reads high, get the treatment to lower it and change/clean your filer and possibly syphon the gravel. Sometimes excess waste or food can cause alittle problems but its not a big deal. However, it sounds like it was the water change that affected the reading so chances are you wont have to do anything. Just give it a few days, keep a close eye on the fish, and switch your water changes to every three or four weeks. Let me know if it continues to read high or if something else goes wrong. I hope this helps. Let me know if you need anything else.