I am going to share a post with you from Seachem's website.
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03-03-2011, 09:54
Re: Cupramine and Prime?
Thanks for the post!
Depending on what type of test kit you are using, you are most likely getting a false high ammonia reading. Here is a quote from our FAQ page on Cupramine and ammonia:
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.
Because Prime, like all water conditioners, is a reducing agent, it has the potential to reduce the Cupramine from the safe Cu2+ form to a very toxic Cu+ form. The best option would be to add Stability to boost your biological filter and get a test kit that can distinguish between total and free ammonia. This will help you determine if the ammonia is indeed the toxic form, which I highly doubt it is, but it never hurts to get a second opinion.

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So you may be getting a false high reading, and like this post was saying, it will be a good idea to add Seachem Stability to your QT. I would still do a water change just to be safe and then add stability after water change. Are you using a sponge filter? Bulk reef supply sells awesome QT sponge filters.