Ph And Filter

[Xraymark]

I've asked this before in a round about way so i'm going to be more succinct.

How low can the PH in your cycled tank go before the filter bacteria stops functioning?

Cheers

 

[DrRob]

I used to know this, but can't remember. What I can remember is that it's very low, but the lower pH bacteria that can do the job are less efficient than the normal range ones, plus you'll end up back in a cycle if you go past a certain point as the "standard" bacteria will die and you'll be getting new ones forming. Brings you back to the don't move the pH quickly issue.

There is data out there about drop offs in function of the microorganisms in a filter below a pH of 6, but they're all from the waste water treatment industry, which is dealing with a different circumstance with constant high SG, high organics, high nitrogenous waste/phosphate waste mixed with good flow.

 

[TwoTankAmin]

That becomes an interesting question as the answer is really relative. If you are asking at what level in the average tank does nitrification essentially cease. One could argue that about 6.0 is the number. And in fact for most tanks the effective number may be closer to 6.5. The standard advice is to try to hold the pH over 7.0 during cycling. How high it sould be is a different discussion.

However, what is going on and what may or may not happen over time is a completely different issue relevant to acid pH levels. There is ample scientific information of nitrification happing at pH levels as low as 4.0. But at these levels, unionized ammonia (NH3) pretty much doesn't exist. The research I have seen was not sure of what the AOB would be using as a substrate. It postulates, but that is far from knowing.

I know in the waste water treatment industry nitrfifcation at acid pH levels is a necessity and there exists strains of bacteria that do it. I know a waste water expert who is very big on keeping wild caught acid water fish and has the most eloaborite water system I have seen in a ptrivate home can get such bacteria. Yes it is commercially available if you know where to go.

I know there are some very talented folks in Europe actually spawning wild altums angels and this takes acid water and cycled tanks. I have seen the pictures and vids and read reports of etc. witnesses who are qualified to know (Ph.D. in biochcemistry and teaching professor).

I have also read instructions for how to get a tank cycled to function in pH levels under 6.0. I think I posted them somewhere on this site. I used them but only needed to keep the cycle at a 6.5 pH so it wasn't as big a deal. But how do you think folks whose tap water is in the low 6s keep fish if they can't get their tank cycled?

Basically, the process involved cycling the tank at 7.0 pH. Once there you drop the pH by 0.2 pH and then dose ammonia. Some of the bacteria will be adversely affected by the drop but others will be fine. The dosing and the waiting allow the resistent ones to multiply. Once you are processing all the ammonia (the bacterial colony has returned to full strength) you drop it again by 0.2 pH and repeat. When heading to pH 6.0 and below, this process can take a long time as each drop may require 2-3 weeks and you may need more than the standard test kits. But it does work.

So as you can see, when you ask that question in the scientific forum, the answer may not be quite the same on the general forums where folks will usually answer between 6.0 and 7.0.

And that is only half the story. Just because nitification may stop in your filter at 6.0 and slow precipitously on the way down there, this does not mean that the bacteria are dead. They are inhibited and raising the pH back up will result in a resumption of nitrifying activity.


References:

Long-term storage and subsequent reactivation of aerobic granules- http/www.sciencedi...960852408002009 you can see the abstract free, read the whole thing but not copy if for $0.99.

Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance- http/aem.asm.org/content/72/6/4283.full - full research report available- click either fulltext or pdf to the right of the abstract

 

[Xraymark]

The reason I am asking is I intend to set up a second tank with an amazonian blackwater biotope. Now my water must be very soft because it drops quite quickly to 6 and maybe lower as my API tester does not go lower in my first tank. I use coral chips in that tank to keep it around 6.4

Now with my new tank I will have loads of wood and indian almond leaves to get the blackwater appearance which are meant to drive the PH lower. So if my tap water is at most 6 then I have concerns about my filter. It looks like I will just add coral chips to this filter as well.

Thanks for the responses

 

[TwoTankAmin]

As mentioned above, I am a member at a wild angel forum. There is a thread there titled "Cycling A Biofilter for Use in Acid Water Aquaria". The article also contains an exchange with Dr. Hovanec. The author of the post contacted him and asked if Dr. H would answer 3 basic questtions:

1. How to get biofilter working at low pH?
2. Can nitrifying bacteria adapt somehow to low pH (i.e. < pH 5.0)?
3. Can a very slow adaption (several weeks/months), serve to help nitrifying bacteria cycled in an alkaline or neuter culture media, work in moderately acid media?

The answers that came back were remarkably similar to the guidelines posted by the author. Unfortunately the angel site is freely viewable in all aspects except for the forums where it is required one be a member just to read. I have never joined another site with such a requirement, but I made an exception for this one due to my attraction to Altum angels. TFF has a policy of not permitting its members to be solicited to join other sites via forums posts and I wont violate the policy. However, if you would like the info, please send me a site PM, and I will send you the info.