Ammonium spike

[Bill T.]

It's an outrage - shouldn't happen - but I have had a slight Ammonium spike (0.05ppm). pH has been between 6.0 & 6.5 for quite a while. I put some shellgrit in the tank about two weeks ago to help buffer the pH which lifted the pH from 6.0 to 6.5.
I did reintroduce 12 cardinal tetras from my "extras" tank about two weeks ago, but wouldn't think this would make much difference.
I have a 240 litre tank with two 2215 eheim canister filters and a U.V. steriliser.
I've done a couple of water changes, washed both filters (in aquarium water) which had a lot of mud in them and started putting "cycle" in for a while. I'm wonderring if there was just a build up of organic material that produced the ammonium? Also, is the theory that pH below 7.0 will eventually erode the bilogical filter (fact or myth?).
Apart from this, everything else looks fine. My two discus pairs are laying down eggs all the time. Also have two corydoras, two bristle nose & four foxes in this tank.
Opinions please.

[Merrilyn]

Just a thought Bill, but have you tested your tap water for ammonia?

We've had some interesting results from testing the tap water recently.

In answer to your question about pH, yes I do believe that bacteria is a lot less active at around or below a pH of 6.5 from my own personal experience.

I'll try to find some more scientific information on the effects of low pH on bio filtration.

[Bill T.]

Thanks Merrilyn.
Haven't tested the tap water for Ammonium, but the "spike" happened after missing a couple of water changes. One day post water change and the ammonium has reduced a bit.
Should the shell grit keep pH a bit higher than 6.5? In the past my pH has stayed at or just below 7.0.

[Merrilyn]

Bill, it depends on how much shell grit you're using, and how old it is. It will also depend on the starting point of your pH. The idea of the shellgrit is to buffer pH and hold it steady. There is no standard rule I'm afraid.

It's very much a case of trial and error.

[Bill T.]

Hi Merrilyn.
I managed to coax my pH back up to a little over 6.5 with a teaspoon of kH with no apparent ill effects. Also, I have been adding some cycle. Now the ammonium reading = 0. Hopefully everything will remain settled now.