A lot of things I see wrong here... First, the cycle could not take 3 weeks, that is nearly impossible. Second, cycling requires some type of ammonia source (food, fish, pure ammonia) and it appears you didn't provide the bacteria with food. Basically you were testing tap water.. which is why you got "good" readings from the LFS, the only thing that should show up would be nitrates.
When you said you set it up 3 weeks ago and "let it run" was that just an empty tank?? No fish or ammonia? If yes, your tank is not cycled and you will NEED to do water changes daily until the cycle completes. Just letting the water run through the filter with no ammonia source is useless. The bacteria needs some sort of ammonia to grow.
I would get rid of the test strips and get an API freshwater test kit (liquid). It is far more accurate. If you get nitrites above .25ppm I would do water changes until it is below that level.
I would read up on the cycling process so you can better understand it for your other tank. Also, do water changes!!!!! The effects of having high levels of ammonia or nitrite is far worse than having them deal with a water change.
Read this
http://www.aquariumadvice.com/articles/articles/24/1/Nitrogen-Cycle-/Page1.html
When you said you set it up 3 weeks ago and "let it run" was that just an empty tank?? No fish or ammonia? If yes, your tank is not cycled and you will NEED to do water changes daily until the cycle completes. Just letting the water run through the filter with no ammonia source is useless. The bacteria needs some sort of ammonia to grow.
I would get rid of the test strips and get an API freshwater test kit (liquid). It is far more accurate. If you get nitrites above .25ppm I would do water changes until it is below that level.
I would read up on the cycling process so you can better understand it for your other tank. Also, do water changes!!!!! The effects of having high levels of ammonia or nitrite is far worse than having them deal with a water change.
Read this
http://www.aquariumadvice.com/articles/articles/24/1/Nitrogen-Cycle-/Page1.html
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