Ph Crash !

[//stuart]

ARGH!

Got a PH crash down to at least 6, and ammonia is now not clearing after 12 hours!

What do I do now?

My cycle threads over here...

My link

Day  Date   PH    PH(high)  Ammonia  Nitrate   Nitrite
55   14Apr  ---   ---       ---      ---       5.0ppm     07:30
55   14Apr  ---   ---       ---      ---       0.0ppm     18:00 + 4ml ammonia@19:30
56   15Apr  ---   ---       ---      ---       2.0ppm     07:30
56   15Apr  ---   ---       ---      ---       2.0ppm     09:00 (2nd check @ 9am) + 4ml ammonia @ 20:30
57   16Apr  ---   ---       ---      ---       2.0ppm     08:20
57   16Apr  ---   ---       ---      ---       0.0ppm     14:20 + 4ml ammonia@21:00
58   17Apr  6.0   <7.4      2.0ppm   20ppm     0.5ppm     09:30

 

[KittyKat]

Large water change and buffer it back up to what it was, then make sure it stays there. A pH crash will always slow the cycle down, so it's best to try and avoid one.

 

[mishka83]

Exactly the same thing has just happened to me!!

Things were going really well until now. My pH is below 6 for sure.

I've just done a 90% water change and it's now at around 6.8 but don't know how to get it any higher.

Kitty Kat, having not done anything to cause this crash, how can it be avoided?

 

[BIG BAD BARRY]

Stuart, update on your cycle log post.

mishka83 - If the ph gets towards 6 then you can either do a water change or dose the tank with bicarbonate of soda to help the buffering capacity (alkalinity).
If you use bicarb then 1 teaspoon per 50L. This needs to mixed in thoroughly and test at 12 and 24hrs to verify and then add carefully to get desired ph.

The below link has some useful info to help understand ph and how it is linked to other factors and its complexity:

http/fins.actwin.com/mirror/begin-chem.html

 

[KittyKat]

Kitty Kat, having not done anything to cause this crash, how can it be avoided?

The only way I can think of is to test the water hardness and watch how that changes.. but in a cycling tank, it is best to just do occasional large water changes.

And you did in fact cause the crash with the addition of ammonia to the water Nitric acid can be formed from water, nitrite and nitrate: the only way to avoid the crash is to not let the nitrite concentration get very high. This is partially why I often recommend a large water change after a few days of nitrite above 5 ppm.

 

[mishka83]

Thanks for the replies, very helpful

 

[waterdrop]

Yes, and I think there's nothing wrong with a double change when you get a big pH crash late in the fishless cycling game. Often a single large change doesn't seem to do the trick as the substrate sometimes doesn't get as thoroughly stirred up. (The collection area in larger cannister filters can also be a culprit for harboring nitrates and their nitric acid sub-component I sometimes think and so the (admittedly heretical) thought of a very gentle water change of the external cannister also comes to mind although that sort of disturbance often causes a day or so pause in bacterial activity just due to the disturbance factor I think.)

~~waterdrop~~

 

[KittyKat]

Yes, and I think there's nothing wrong with a double change when you get a big pH crash late in the fishless cycling game. Often a single large change doesn't seem to do the trick as the substrate sometimes doesn't get as thoroughly stirred up. (The collection area in larger cannister filters can also be a culprit for harboring nitrates and their nitric acid sub-component I sometimes think and so the (admittedly heretical) thought of a very gentle water change of the external cannister also comes to mind although that sort of disturbance often causes a day or so pause in bacterial activity just due to the disturbance factor I think.)

I agree. In fact, I do not treat pre-filters as bio media at all, so would quite happily give them a decent clean, even though that may prolong the cycle.