Ammonia Reading High after 98% water change

My qt was emptied down to about 5 gallons after the fish in qt didnt make it. Yesterday I then emptied the tank as far as I could probably less than 1 gallon left in the tank (20 gallon tank), I re filled with 15 gallons of brand new mixed water. My ammonia readings are .5 after all this with API test. The only thing in the tank is a piece of sponge from a established tank. Trying to figure out if the ammonia readings could still be high from a trace amount of cupramine that was in the tank. I added a seachem ammonia alert badge to see if it reads ammonia also. Any ideas?

 

This might be a dumb question but did you test your "new" water before you added it to the tank. Also depending on what chemicals you use to treat the water can cause a high ammonia reading.
I would:
1) make a 1gal container of water and test it.
2) if it tests no ammonia, then
3) add one of your treatment chemicals at a time and retest the water after each chemical
3) If after all that the water still tests neg for ammonia then it is something in your tank.

I would start there

 

The water used is the same water I use for all my tanks and water changes. I didnt test it for this water change specifically but it always reads 0's for everything. There were no treatment chemicals added to the QT after all the new water was added. The tank did have cupramine in it but again, less than 1g of old water remained when the 15g of new were added.

 

Any more ideas? I'd like to pick up another fish I have had on hold at the LFS. But am trying to decide if I do another complete water change if I will end up with a high ammonia reading as well. The ammonia alert is not showing high ammonia. Less than .05

 

Get another ammonia test kit to verify the first test. Did you aerate the new water for an hour before putting it into the tank? Salt mixes gas off ammonia when mixed with water.

 

This is from Seachems site on their FAQ section:

Q: I'm using Cupramine™ and my ammonia test kit is showing ammonia off the scale. What is going on?

A: Ammonia test kits can not distinguish ammonia from the amine based complex present in Cupramine™ and will therefore give a false high reading for ammonia while using Cupramine™. Our Ammonia Alert™ and MultiTest: Free & Total Ammonia™ test kit do not suffer from this problem as they utilize a gas exchange technology that can distinguish ammonia from amines.

As long as you use some Prime from seachem it will detoxify your ammonia levels. The badges that they sell are crap IMO. I went through this same thing not too long ago, and was getting off the charts readings for not only ammonia, but nitrites as well. I just did 20 to 30 percent water changes and kept dosing prime and did not lose any fish. It was from the lack biological filtration, because you can't use anything but a sponge, and as soon as you dose the cupramine it all but kills that existing bacteria that you have.

 

The ammonia test was verified with my API ammonia test and a lfs ammonia test both reading .5 ppm. as per seachems website prime should not be used with cupramine I do believe ( using my phone so to lazy to verify). there was less than 1g of old water which had copper in it so could it cause this high reading still? My water was not aerated. But sat after mixed, and the tank its in is aerated. I never aerate my water and show 0 ammonia.

 

In regards to the prime, answered by seachem support
Cupramine and Prime? - Seachem Support Forums

 

Not sure if you got the answer you wanted...two things that I have found to give readings in newly mixed saltwater are 1) Salt mixes have varying levels of ammonium compounds...these will give your test kit an ammonia reading but are not harmful to fish and other critters. 2) If you source water is treated with chloramines your RO/DI may not be configured to removed it. The carbon in your RO/DI will strip away the chlorine component but that leaves the ammonia which most RO/DI's are not good a dealing with. In this case you have true ammonia which is a concern.

 

In response to any thoughts that the new water is the problem the same water from my rodi unit had been mixed and tested for ammonia before and showed 0. Still not understanding what caused the high ammonia reading after adding 15 new gallons to 1 old gallon that had a small amount of cupramine