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I am currently cycling a new tank and according to my ammonia test kit it states that when the PH of your water is below 7 then the ammonia is present as non-toxic ammonium. The PH in my tank is around the 6.5 mark due to the water in my area being slightly acidic. To what extent does this mean that my fish won't be as susceptible to ammonia poisoning?

gmanoz what fish are you using to cycle with? Different fish will respond to ammonia differently. Increasing surface agitation can also help reduce the effects of the ammonia and later nitrIte spikes on the cycling fish.

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I copied this from another thread I wrote, so if it looks familier to someone, feel free to skip right over it . At higher pH's, the ammonium-ammonia equilibrium is shifted more toward ammonia, much more toxic than ammonium.

Ammonium + Hydroxide Ion <--> Ammonia + Water

NH4(+) + OH(-) <--> NH3 + H2O

At lower pH, there is more H+, so more H+'s attach themselves to ammonia to form ammonium which is less toxic than ammonia. Our test kits only measure the total amount of ammonium and ammonia. So, the same amount of ammonia is more dangerous at a higher pH.

But, ultimately, the cycled tank should have none whatsoever, so this is not really a concern.

But, it should be stressed that the system is always in equilibrium... that is, there is always both ammonia and ammonium. So, yes, safer at low pH, but not 100% safe. This is why many members have taken to fishless cycling, either with pure ammonia or by maturing a filter in a running tank.