Helpppp! 7 months and tank isn't cycled?!

[twentyleagues]

I don't think that's the case. I've never had the pH drop during a cycle but my kh is kinda high out of the tap 11dkh. But even when I was young I didnt have ph drops in cycling tanks.

I think your ph dropped causing your bb to decrease effectiveness. Then you added water during a water change and ph rose bb woke up and went nuts and now your ph is down again and bb is zzzzz.
I could be wrong?.....

 

[robham777]

I don't think that's the case. I've never had the pH drop during a cycle but my kh is kinda high out of the tap 11dkh. But even when I was young I didnt have ph drops in cycling tanks.

I think your ph dropped causing your bb to decrease effectiveness. Then you added water during a water change and ph rose bb woke up and went nuts and now your ph is down again and bb is zzzzz.
I could be wrong?.....

I think this is pretty much spot on. I have a PH of 7.8+ out of the tap, but only 4dKH. If I slack on wc's my ph can bottom out the api scale for the low range and I will get an ammonia reading. I have 12 tanks running and probably 12 different ph readings. I won't claim to completely understand the chemistry and biology of the relationships but have experienced the same results as the OP. I suggested making changes slowly mainly because if the tank has been running at a low ph for 7 months, there is no way to know what level of bacteria is present to handle the changes. With the increase in nitrate and decrease in ammonia it would seem there is probably a sufficient colony in place. With neutral ph from the tap it would probably a good idea to experiment with some type of buffering agent like crushed coral and get a gh/kh test kit to monitor what is going on.

 

[tarheel96]

The study below sheds some light on the relationship between carbonate alkalinity and nitrifying bacteria.

"The effect of alkalinity on nitrifying biofilm activity was determined by collecting ... various initial carbonate alkalinity concentrations and (2) with four types of available alkalinity: carbonate only, phosphate only, phosphate plus hydroxide, and phosphate plus carbonate ... Ammonia, nitrite, and nitrate concentrations were measured ... The type of alkalinity, carbonate versus phosphate, affected nitrification rates. When the carbonate alkalinity was less than 45 mg/L, nitrification rates were impaired regardless of the total alkalinity concentration. This effect seems to be independent of pH for the range of 6.92 to 7.99 evaluated here. This suggests that in addition to neutralizing the acid generated by the nitrification process, a minimum level of carbonate alkalinity is necessary to meet the ammonia-oxidizer's inorganic carbon requirement for cellular synthesis and growth."
https://www.researchgate.net/public..._Concentration_on_Nitrifying_Biofilm_Activity

 

[Jay335]

Did a 40% change yesterday and this morning PH dropped back down to 6..
Ammonia at .25-.50 again going to start dosing with baking soda.

I also replaced the mechanical filtration media during that water change.