Understanding toxicity impacts between pH level and Ammonia.
How does pH affect the toxicity of ammonia?
 

Table 1 - the Nitrification and Ammonification process.
 
The Ammonia reading you get from test kits is actually the sum of Total Ammonia - which is made up of Ammonia NH3 + Ammonium NH4.
At low levels of pH (lower than 6.0), ammonification occurs. Remember, pH is an inverse count of Hydrogen (H). At low pH, you have more Hydrogen. At high pH, you have less. At these low levels of pH (high acidity), the ammonia NH3 'absorbs' (for lack of a better word), an extra Hydrogen ion -> becoming NH4 or ammonium.
The reason Ammonium is less toxic to fish and shrimp is because NH4 with that added Hydrogen H ion is now less permeable to the gills of fish & shrimp. NH4 is also excreted across the gills via a carrier mediated process in exchange for sodium Na+.
Ammonia toxicity is also influenced by temperature:
The lower the temperature the less toxic it becomes. Or to put it another way - NH3 toxicity increases with temperature and pH.
    Percent NH3 of total ammonia Temp  pH 6.5 pH 7.0 pH 7.5 pH 8.0 pH 8.5 20C / 68F 0.13 0.40 1.24 8.82 11.2
25C / 77F 0.18 0.57 1.77 5.38 15.3
28C / 82F 0.22 0.70 2.17 6.56 18.2
30C / 86F 0.26 0.80 2.48 7.46 20.3
Table 2. Un-ionized NH3 as a percent of total ammonia (by temperature and pH).
 
Assuming a temp of 28C and a pH of 7.0 - if 5ppm of ammonia is present this results in only .03 ppm ammonia.
However, in a Tanganyikan Cichlids tank with a pH of 9.0, that has a Total Ammonia of 5 ppm, your ammonia level is 2.06 ppm! This now become toxic for the fish.
 
But, at a pH of 6.0, and 10 ppm of Total Ammonia, the ammonia is only .007 ppm. Even though we have MORE ammonia.
So be cautious when performing water changes in a low pH tank, as the low pH has an adverse affect on the nitrifying bacteria that converts ammonia to nitrite.  Because of the acidity these bacteria populations can drop so low that any change in alkalinity can cause the Total Ammonia reading to rise quickly.  While the pH stays low the Total Ammonia reading is nearly all ammonium, but if you do a water change or add an alkalinity buffer to the system, the ammonium can be quickly converted to ammonia, potentially causing ammonia poisoning.
It is good to note here that, as per the very top picture (table1) ... nitrifying bacteria that convert ammonia NH3 to Nitrate (NO3) does NOT convert Ammonium NH4 to a less toxic form. The bacteria isn't present in sufficient amounts in such low pH environments to process it. Ammonium NH4 is ever present in a low pH tank that has living creatures in it. NH4 is in there ready to be converted into NH3 at the first sign of added alkalinity during water changes. Hence, why we always tell you to match water parameters and add it into the tank slowly (drip it in if you can), don't dump in buckets of new water all at once.
So in summary, the combination of low pH (<6) and cool temperatures that the shrimp live in can mean that high ammonia levels are not toxic to them. But be careful !!! Any change in the pH buffer that increases alkalinity will cause the toxic ammonia to immediately convert from NH4 to NH3.
 
There you go. Hopefully that is a more precise explanation to aid your understanding. 
The ideal spot to be is just above 6.1 to 6.5, where bacteria still function, and ammonia is less toxic. Along with the cool temperatures some shrimp (or fish) live in,  is the best environment to be in to minimise ammonia poisoning.
I wonder how many times our shrimp die in hot temps, (say due to hot weather ... maybe even a broken heater) not because of the heat, but because our low pH tanks have not enough functioning bacteria to cope with the sudden change in toxic NH3 ammonia due to the rise in temps??? Food for thought.

Hello,
So the problem is, that my pH is always rising and settling in the range of around 6.8, but I fail to understand why and I hope you will clarify the problem for me. Let's get into details:
I am running inert substrate tanks, which have the following parameters: pH 6.7-6.8, GH 5-6, KH 0-1, TDS ~125.
My routine is that I do weekly water changes of around 20%. The water for changes is RO water + salty shrimp GH+ + Azoo Triple Black Water (which is basically a tannins and humic acids extract)+ Azoo Ph Lower, and I usually adjust the pH to around 6.0-6.2 as I want to keep it acidic, but the pH just won't go down lower than 6.7(to be exact - If I would add peat, or a lot of those acids, then sure it would go down lower, but after some time it always comes to it's usual 6.8 range). I also adjust the pH of the top-up water, which is RO + Triple Black Water.
As I am adding a lot of acids into the water I thought the pH should stay acidic, unless there is something that absorbs those acids.
So I did a test - I have prepared my usual bucket of water, re-mineralised it and adjusted pH to below 6.0 and let the bucket be. After around 24 hours I have measured the pH of the water in the bucket and, the pH was back at around 6.6. So it raised a lot. Once again I lowered the pH to below 6.0 using Triple Black Water only, and after another 48 hours the pH was again 6.8.
So why is the pH rising ? I understand that with kH 0 there is nothing to buffer the water, but since I am adding acids into the water and there is nothing that could absorb them what causes the pH to raise ?
Thanks !

I am new to keeping shrimp and was hoping someone can help me sort through some issue with the water parameters of my tank. The tank is a 4.6 gallon cube, that runs between 72 - 74 (22.22 - 23.33) degrees, 0 ammonia, 0 nitrates and 0 nitrites. It has been cycled and running since December 2015 but about a month back converted to a shrimp tank (removed the fish, did a 100% water change and added sponge over filter). Current inhabitants are a nerite snail and 1 RCS.   I initially had 3 RCS, but lost two. I believe this was due to them trying to molt as they both had white lines on their back, but were fine the day before (one after 7 days and another after 12 days). I also have some java jerns, java moss, dwarf sags, crypt wendetti, and some floaters.
Current water parameters:
TDS: 166ppm
GH: 1.7
KH: 0
My PH is also low (6 something if I recall but can measure this again if needed). I am using tap water that I add prime to that is then place in a rubbermaid with a powerhead until I need to do top offs / water changes.  So far all I have done is top off on the shrimp tank. My plan is to pick up some Salty Shrimp and add that to the tap water to raise GH and KH. I believe I should be shooting for a GH between 6-8 and KH of 2-5, with a TDS between 80 and 200. I also plan to add some iodine twice a week to try and address the molting issue.
Does this seem reasonable? Any additional changes I should be making or consider? Once the water parameters are in order, I would like to add some additional RCS to the tank.
 
 

Hi everyone, I have spent some time searching (unsuccessfully!) for any threads set up to address how to naturally and chemically treat the more important water parameters. Obviously I'm not talking about temp, but the PH, TDS, KH and GH levels are the ones I'm most interested in. Now I'm country based so the only water I've got access to is R/W and bore (perfectly drinkable from the pump itself, no brackishness) which I have used for 4 of my 6 tanks (tropical and a few lower grade cherries). But I want to better hone in the water condition as best I can so any tricks to raise lower the above parameters naturally or if need be chemically. Or if anyone knows/finds a link, anything will be appreciated.
Had put this in the pinned "Shrimps 101" but will try to delete it as it's probably better as a separate post.
Being rural makes water choice difficult and some of the values I've tested are way out, hence why I'm seeking advice.
Cheers all.