live plant

[HarleyK]

Howdy,

I just thought I'd clarify something about live plants using ammonia as I recently had a discussion about it. Just in case anyone else gets into a discussion about whether plants use ammonia and someone decides to tell you they don't use ammonia(NH3) know that what plants actually use is ammonium(NH4). However what we actually refer to as ammonia in our fish tanks is the total ammonia nitrogen(TAN). The majority of the total ammonia nitrogen is actually ammonium(NH4). So if anyone decides to tell you plants don't take ammonia, they're actually refering to the less than 1% of NH3 that composes the total ammonia nitrogen in our ammonia test reading. just thought i'd clarify because I recently got into a discussion where someone very rudely told me plants do not use ammonia on another forum.

You make some very good points, but I'd like to clarify a couple of points about the NH3/NH4+ equilibrium:

1. We do NOT refer to TAN when we talk about ammonia in our water. Most test kits detect ammonium. You then use a pH table to determine the concentration of free ammonia, because that's the highly toxic brother.
2. As you stated absolutely correctly, ammonium (NH4+) is generally the most prevalent form in our tanks. However, that's pH dependent. In a Rio Negro tank with pH 5.1, NH3/NH4+ is virtually non-toxic because the equilibrium is shifted to NH4+. Using the Henderson Hasselbalch equation, the ratio is roughly one to one million. In a Tanganyika tank with pH 8.4, the same NH3/NH4+ concentration is far more toxic because the equilibrium is shifted to free ammonia, ratio one to 6.5 !!!

To the OP: In theory, plants do take up ammonia (think agricultural fertilizers), but in reality, in a tank with functioning biofilter, they are massively outcompeted by bacteria. There little to no ammonia left for the plants to take up. Plants rely mainly on nitrates in our tanks.

Just thought I'd set the record straight
HarleyK

 

[carsona246]

Thanks for the clarification. I've been trying to get some clarification on tan, but my test kit actually reads the sum of NH3, and NH4(I think) so I just assumed that was the case. Just out of curiosity, how dangerious is ammonium? I have a ph of 6.4 and my tank temp is usually at 18 C, according to this calculator http://www.petgoldfish.net/ammonia-calculator.html I would still not even have %1 ammonia if my test kit which claims to read both ammonia/ammonium read 8 ppms.

 

[HarleyK]

Ammonia/ammonium is not good at any level detectable by hobbyist kits. If you can detect it, then you need to do something about it. It is a sign that your biofiltration is not working properly. Or your test kit has gone bad.

HarleyK