Ph Kills My Cycled Tank!

[doresy]

Had a strange happening.

Any followers of my posts will know of the tank I have been cycling (right hand tank in signiture)
I live in a reletivly hard water area.
The 'rocks' in the tank are artificial, bogwood is real and so is the Java Fern

My tapwater is 7.4 ph.

Cycling took around 3 weeks with a matured media kick-start.

Have continued for 4 days after 0-0 was achieved for ammonia/nitrite.

Suddenly, after 5th day ammonia/nitite only dropped to 1.0 amd 0.25 respectivly.

Checked ph and it had gone to 6.0 so tonight did a 90% waterchange, added the usual 5ppm ammonia.

Nitrite was 0 and ph 7.4.

Can't explain the ph crash but it obviously affected the cycle.

 

[Schmill]

Apparently the cycle itself can sometimes affect the ph, (although I can't remember which way, I think down) due to the nitrifying process, and the bogwood can lower it a bit as well, but as you are in a relatively hard water area this seems unlikely, I wonder what it was. Still at least the water change has given it a kick hopefully, keep testing, keep an eye on the ph, and keep your fingers crossed

 

[rdd1952]

A pH drop really shouldn't affect the bacteria that were already present. They should have continued to process ammonia and nitrite as before. Low pH just slows or inhibits additional reproduction. It is odd that it happened that way though.

 

[Bignose]

The end products of the cycling process are acidic. Ammonia (NH3, basic) is converted into nitrous acid (HNO2) which is converted into nitric acid (HNO3). So, of course the pH is going to drop. The real question is how much buffering capability your water has. While not common, it is possible to have water that has high GH (general hardness) but a low KH (carbonate hardness). A high KH is what you need to have high buffering capability.

 

[doresy]

The end products of the cycling process are acidic. Ammonia (NH3, basic) is converted into nitrous acid (HNO2) which is converted into nitric acid (HNO3). So, of course the pH is going to drop. The real question is how much buffering capability your water has. While not common, it is possible to have water that has high GH (general hardness) but a low KH (carbonate hardness). A high KH is what you need to have high buffering capability.

Thanks for the replies and in particular 'Bignose'

Well, after last nights massive water change all was great this morning. Ammonia was back to a bright yellow zero and the nitrite and lovely shade of blue (isn't that blue a lovely sight after a long cycle! )
PH holding at 7.4. Don't have room in the filter for coral sand so best way to bring up the ph to a bit less acidic, say 8.something?

Pumped the ammonia back up to 4ppm so will continue as before. (Mrs D. has plans for me untill after next weekend and unfortunately they don't include hunting for fish I hate Christmas!!.....(not really, it just gets in the way)

 

[OldMan47]

I don't understand the desire to get pH to 8 but you can do it with baking soda if you really feel you must.
When cycled, you will want the tank at something near your tap pH so that you can put fish into it and not worry about rapid pH and KH changes coming from routine water changes.

 

[doresy]

I don't understand the desire to get pH to 8 but you can do it with baking soda if you really feel you must.
When cycled, you will want the tank at something near your tap pH so that you can put fish into it and not worry about rapid pH and KH changes coming from routine water changes.

Hi, points taken

The desire to get the ph to 8 or above was for my first idea of getting Malawis, I forgot that that plan had been scuppered due to tank size. You are right in keeping ph & tap water close to the same.

Tonight was still showing 0.25 for ammonia and nitrite so added a little less ammonia, ph still holding at 7.4 though. See what gives in the am.