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Discussion Starter · #1 ·
I am 3 weeks into my cycle, at a point where it takes ~48 hours for my filter bacteria to process 2-4 ppm ammonia into nitrate.
July 12, I added 2 ppm ammonia into the water (it was at 0 ppm). 26 hours later, when I measured ammonia, it was exactly the same. I found this extremely worrying. On July 12 I went to the pool, and briefly put my arm in the tank before showering, though it was dry. Is it possible that residue from pool chemicals could have killed off all the bacteria in the filter? If not, what could explain the sudden lack of change?
 

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What are your results for nitrite and nitrate?

I don't think your unwashed dry arm after a pool visit should have impacted the cycle.
 

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Discussion Starter · #3 ·
My nitrite is 0 and my nitrate is around 90 ppm. I did see nitrite earlier in the cycle. My nitrate is very high because I have not changed water since the start of the cycle.
 

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Discussion Starter · #4 ·
Update: I just tested the pH of the tank water, and it is below 6.0. I'm not sure why, since my tap water is pH 7.4. The acidity of the water may have killed the bacteria, but I have no idea why it dropped so far...
 

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Since you did see some nitrite reading AND your nitrate is so high, what I would do is a series of water changes to bring your nitrate down to 20 ppm.

I don't know what is going on with your pH below 6.0. Have you ever tested the KH of your tap water AND also left a sample of your tap water out for 24 hours and tested the pH to see if it drops?

Do you have any other aquariums and if so, what is the pH of those tanks?
 

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Discussion Starter · #6 ·
Ok so I have previously let my tap water sit for 24 hours before testing, because of recommendations on other forums to do so, and confirmed the same pH. I just tested my tap kh and it is pretty low, between 50 and 100 ppm.
Most recently, I just did a 70% water change to lower nitrate and acid concentration. I also added Malawi Victoria buffer (which I keep around) to buffer the pH.
 

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sorenH said:
Update: I just tested the pH of the tank water, and it is below 6.0. I'm not sure why, since my tap water is pH 7.4. The acidity of the water may have killed the bacteria, but I have no idea why it dropped so far...
This is definitely why. If you started at a 7.4 ph and are now below 6.0 I would say with 90% confidence that is what killed your cycle. Do you have a test kit for hardness (kH especially)? Test for it and see if its really low, that might be why you lost so much pH.
 

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Discussion Starter · #8 ·
I already did a water change to get pH up, so I'm not sure what my KH was before. Right now my pH is 7.4 and my KH is 5 dKH using the API test kit.
I have heard that low pH can make the nitrifying bacteria dormant. Is there any chance they are still alive, or do you think I will have to start again from square one?
 

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If I am following correctly, your bacteria were bringing ammonia to zero in 48 hours and because it did not go to zero (or change at all) in 26 hours you worry that your cycle is stopped?

What happened to ammonia after 48 hours?

Seems like normal progress to me. What temp are you keeping the tank at?
 

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Discussion Starter · #10 ·
Right now ammonia is 1.5 ppm, nitrite 0, nitrate 40. I dosed 2 ppm ammonia 48 hours ago, but did a 50% water change last night because of the pH dropping below 6. After I changed the water, I added ammonia to about 1.5 ppm, which has not yet changed observably.
I was worried about no change in 26 hours, but identified that the problem was low pH. However, I'm not sure how far the pH crash set me back since I don't have a lot of experience.

The tank is at 82°F.
 

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I know this is kinda older post but my 2cnts. Growing BB will eat the Kh right out of your water, crashing your PH. When your really cooking with a new tank and it's burning the ammonia fast your BB need building blocks to form, your Kh is one of those resources they need. I use a PH monitor I know my running PH so I add ammonia the PH goes up you can watch the BB clean the ammonia as it lowers. If it lowers below run point do a water change to refresh your Kh. Ammonia to nitrite grows faster than your nitrite to nitrate so once your using up that much KH skip to every other day for ammonia this gives the other bacteria time to colonize the surface area instead.
 
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