03-06-2011, 12:31 AM
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Originally Posted by Byron
To answer your initial question at face value, yes; in acidic water (pH below 7), ammonia automatically changes to ammonium. Ammonium is basically harmless. Nitrosomonas bacteria still consume ammonium as ammonia, so the cycle will establish normally. Live plants if you have them prefer ammonium as their source of nitrogen, so even better especially in new tanks [won't delve into this topic now]. Test kits like API's tread ammonia/ammonium as ammonia, so it will still show "ammonia" although it may be ammonium.
However, if you are fiddling with water chemistry to lower the pH, there is a real danger in this. If the pH should rise back above 7, the ammonium immediately changes back into toxic ammonia. This may be sufficient to stress the fish, or even kill them if high enough. This can occur during the next water change if the tap water is basic; the tank can shift up in pH quickly. Which brings me to the pH adjustment.
Unless this is done naturally, this is highly dangerous with fish in the tank. The pH of water is largely determined by the hardness. The carbonate hardness (expressed as KH) acts as a buffer to prevent pH shifts. Adding any chemicals to lower the water will temporarily lower the pH, but if the KH is sufficient to buffer the water it will rise back up again. Aside from the ammonia/ammonium issue, the fluctuating pH is very stressful on all fish, and should be avoided. Another issue is that the water can suddenly be overwhelmed with the chemicals and a pH crash can occur. This often seriously harms the fish internally, and also may kill them outright or down the road.
Safe ways to lower pH naturally will work, but the hardness of the tap water is a factor that must be addressed. This issue also i will not delve into here.
Thank you, ver informative. Yes the tap water is really high, like 7.8. I usually add some drops of pH down with conditioner in the bucket before pouring it in the tank. I did not know that about the hardness of water though. I'm pretty sure we don't have hard water but I will look into that, thank you.