Confusing Parameters

[G S P Freak]

Ok, so I just got the API master test kit for Christmas, YAY!, and I seem to be getting odd results...
First day I tested, I got 0.25 Amm, 0 nitrite, and ~40 nitrate. I didn't understand the ammonia, as I have had this tank set up for a few months now, so I did a 75% wc, which was I was due to get done anyways. I do a pwc of 75% or so every week. I tested the tap water for ammonia, and it tested 0 ammonia. I use prime every time I do a water change, my tank also has 4 tiny marimo moss balls, a small java fern, and a windelov java fern.
So, after the water change, I tested again, and got the SAME EXACT RESULTS, what's up? Anyone have any idea, I'm stumped.

[purplecandle]

make sure you are really, really shaking those bottles and check the expiration date if the kit. also are you vacuming well?

[defool89]

You may have rotten food deep in the subtrate and or filter.

[boosted23]

did you test right after the water change with prime? or are you waiting about a half hour? if you dose prime more than recommended for the amount of water i read that prime can give a false positive. here is a link from seacham about this.
http://www.seachem.com/support/FAQs/Prime.html

[RTR]

Clarification: Seachem's Prime does not really give "false positives". Most hobby test kite are based on out of date water chemistry and cannot differentiate between ammonium ion (NH4+) - which is harmless, and dissolved ammonia gas (NH3) - which is toxic. There are at least a couple of test kits which can and do differentiate between the two form, but they are not user friendly IMHO. Seachem does offer one of those kits.

[G S P Freak]

It's not expired, I checked, I follow the directions closely, and I also have to admit I have not been vacuuming as properly as I should have the last few PWC, but last water change I did vacuum really good, tumbling the substrate in the vacuum and vacuumed up a bunch of gunk. I tested the next day, so waited way more then a half hour after dosing with prime. I'm aware it also shows ammonium when testing, so is it possible that this is what's showing up? I see no sign of distress among my fish, and my F8 seems to be as content as usual. I'm just worried about the ammonia test, but again my fish seem to be fine.

[RTR]

The test kit being well within date has nothing to do the fact that it is incapable of reading the difference between ammonium ion and dissolved ammonia gas. It is simply that he chemistry is not appropriate for current water handling. Few LFS understand this, and the old-fashioned test chemistry just is not good enough for current water management. That causes no end of confusion.