Free Ammonia vs. Total Ammonia


My test kit tests both... what's the difference and which should I worry about?
The story:
I've had my tank up for 2 months. It's a 55gal. About 50lbs of sand, 50lbs of base rock, and 10lbs of live rock. I started cycling the tank 2 months ago. The ammonia & nitrite spiked and nitrate started going up... I added some snails, crabs & a green chromis a little too early and caused another mini-cycle, which the chromis didn't make it through. Now, my ammonia indicator on the tank and the TOTAL AMMONIA test kit both say zero, nitrite is zero, and nitrate is around 3-5. I have lots of diatom algea and the hermits that I have left are all doing great. However, my FREE AMMONIA test kit is still reading around 0.1. What's the deal??


Well-Known Member
There are two types of ammonia, as described here . As the link says, free is the most important, and your levels, if true, could present a small problem. First, check the accuracy of the kit by taking a sample to your lfs for verification. If the level is accurate, you should wait until the levels fall to zero. Since your hermits and other inverts are doing ok, I suspect that the kit cannot differentiate 0.1 from zero, and your tank is completely cycled, but why take chances.


Thanks for the reply...
I don't have a LFS... I live over an hour away from the closest place that sells even a small amount of saltwater supplies. Most of what I do is online, which makes places like this so important!
How accurate are the hang-on ammonia indicators? The fact that it shows no ammonia and my test kit shows a little bit makes me wonder which is right. I would trust the test kit over the $3 indicator, but since everything is fine and my nitrite & nitrate have both spiked and gone back down TWICE now is making me leary of the kit. It's the Seachem Multi-Test Marine Basic kit. I thought Seachem was supposed to be a pretty good brand?


Woops, I wrote that wrong in the original post. It's the TOTAL ammonia that's between .05 & .1, not the FREE ammonia. But only on the test kit, not on the ammonia indicator.


Active Member
I'd chuck the hang on indicator. Get another test kit and/or do some water changes just to be safe. Try testing a bucket of make up water that you know has zero ammonia.