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Discussion Starter · #1 ·
Hiya. I set up a 15 gallon tank around 40 days ago and did a fish in cycle (my partner came home one day with a Betta in a cup). I planted heavily with mostly foreground plants, carried out regular water changes (usually 25% or more daily), and tested my water daily. I saw my ammonia levels register, then nitrites began to register, and some nitrates (but only to 5). They didn't have the nice bell curve that cycling charts show, because I was changing the water a lot to try to keep levels down for the fish. After picking up nitrite readings (usually .25 or .5) for about a week, I added a DIY c02 setup and after a few days I stopped getting nitrite readings, but would still pick up ammonia. I realized my pH dropped to 6 or below, and thought it might have stalled or killed the biological filter, so I added crushed coral in my filter to boost my pH to about 6.8, where it has stabilized. After a few days I began to see small amounts of ammonia at around .25, but some days I would get a reading of 0. I have stopped doing daily water changes to see if that helps, but even when I wait 2 or 3 days my ammonia only gets to around .25, and nitrite is not going back up. My nitrate is steady at 5. It's been two weeks since I added crush coral and stabilized my pH, and I'm in a holding patter where some days I have no ammonia, and some days I get a reading of .25. Still no nitrite and nitrates at 5. I'm wondering if anyone else has run into something similar. Did I kill off my biological filter with low pH and the cycle is slowly trying to restart? Am I doing too many water changes? Did my tank cycle but I'm getting ammonia readings from something else? Did my tank never properly cycle? Any ideas on what I can do to figure out what's going on. Thanks in advance for any advice.
 

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So I've been seeing some stuff like this on a saltwater forum. API Ammonia test kits have a bad habit of putting up false positives of .25 when in actually it's a reading of 0. If you have an API test kit, it may be worth doing a false positive and false negative test. Take water that you know has 0 ammonia (like distilled/mineral water, etc.), and water that you know has .25 ammonia (said water with ammonia added to the appropriate amount). And then test appropriately.

But in all likelihood, I'm willing to bet that your tank is cycled.
 

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My understanding / experience of a low pH drop during cycling (in my case due to active soil pulling it waaay down) was that it slows the development of the bio-filter, but does not kill it.

As @ichthyogeek says, API ammonia tests frequently give 0.25ppm "false" reading in cycled tanks. Some weeks / tanks I get 0ppm, others I get 0.25ppm, and haven't been able to find any rhyme or reason behind this. Every time i see a 0.25ppm reading, I add a good dose of bacteria though, just in case.

Seems like it's time to ease off the big water changes and begin to let the tank stabilise and settle. Maybe consider adding Prime (or similar) dechlorinator every day / every other day if you are concerned as this will detoxify any ammonia that is present for 24-48 hours whilst your bio-filter processes it. Also, thankfully, ammonia is mostly in its less toxic form at low pH.

Out of interest, what is your substrate? If active soil (e.g. Amazonia) it could well leach ammonia for several months which may be what your ammonia readings keep popping up with low levels if this isn't actually a false positive. Disturbing the substrate (planting, doing water changes, etc) might well be mixing things up and give a fresh release of ammonia.... maybe.
 

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Discussion Starter · #4 ·
Thank you both for weighing in. I do use an API test kit and I just tested some Fiji and some tap water and they read around .25 ammonia, so I think you're right @ichthyogeek, it may be the test kit. Thanks for turning me on to that.

And @en7jos, I do use Amazonia, but wouldn't my biological filter be able to adjust to this over time? I understand that a large disturbance might kick some up, but I thought that over time the tank would adjust.

Thanks again to both of you, much appreciated.
 

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I tested the water in a couple of my shrimp tanks last night and got ammonia readings of 0.25 and 0.50 ppm with my API liquid test kit! Wow - not good (these are well established, well cycled tanks). So tested my RO water and came out very yellow for 0ppm, hence not an issue with the chemicals. Retested the 0.5 ppm tank with a brand new test tube and it came out yellow (0 ppm) so I think that it is contamination in the test tubes that is causing the false positive ammonia results, at least for me. I rinse the tubes well in water, filling and tipping out multiple times with a strong jet of water, but I don't have a brush to clean inside.

So I have a feeling that a slight amount of residue from whatever test the tube was used for last time (I also test nitrite, nitrate, phosphate, GH, KH and pH all using the same API test tubes) can cause the ammonia test to give a false positive. To confirm this, I have now marked two new tubes to only use for the ammonia tests and will see if I get any more false positives going forward. If not, then I'm pretty sure that it is residue chemicals from one of the other tests that causes the ammonia level to read at 0.25 or 0.5ppm when really it is zero.

Regarding the Amazonia soil, yes, sure your bio-filter will grow to process whatever ammonia the soil is producing. Problem is when there is a sudden spike in ammonia levels (dead fish or snail, disturbance of soil releasing a waft of ammonia, etc) in which case the bio-filter is temporarily over-whelmed. The capacity of the bio-filter grows to match the normal ammonia input into the tank and needs time to grow when ammonia levels increase (adding more fish, increased feeding). But it is never going to be able to cope with big ammonia spikes.

When in doubt, I add Seachem Seed (bacteria) to help boost bio-filter capacity and Seachem Prime (detoxifies ammonia and nitrate for 1 or 2 days) to give the filter time to do it's thing. I tend to do this daily when adding new livestock to a tank as a safety net since it is hard to overdose either.
 

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High levels of ammonia is also toxic to beneficial bacteria! I believe that Amazonia Aquasoil must have several water changes before a cycle can begin.
 

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It's hard to know with the API tests but I am frequently running multiples if I get a reading that surprises me. So if I get an ammonia reading, I would immediately run a second. I had it happen that the second test then shows no ammonia.

One untested hypothesis I have is the inconsistency of results might have to do with the drops from the ammonia test kit bottles, that if you don't have exactly the same amount of 8 drops from both bottles it might throw a positive. So for example if you miscount or perhaps malform a drop (e.g. bottle touching the side of the tube, or not perfectly vertical or other factor that results in a larger or smaller drop), then maybe it throws a false ammonia reading.

All of these API tests are like that. I was testing phosphates last night, had to do 4 tests back to back! First one came out at 1ppm which was a complete surprise since I have added far less phosphate. Ran another that came out 0ppm, was off the chart yellow (freshwater starts at green), then ran two more that came out at < .25ppm phosphates, which was more believable. I assumed my correct reading was the last two and somewhere between 0 and .25ppm.

Another thing I have just started doing to hopefully get more consistent test results, is after cleaning, do a final rinse of the API test tubes with distilled water so there isn't any tap water residue drying on them. I got one of those medical squeeze bottles with the bent straw top, filled that with distilled to final rinse off measurement equipment after cleaning. I learned that trick in a lab a long time ago, we would final rinse everything in distilled.

To answer your question of crushing a cycle, I don't think that is possible just by going a little too acidic. I think its completely possible to injure some specific bacteria strains in the mix that do not like low pH and thus temporarily weaken your biofilter. I have a new tank and have been using both Seachem Stability and Seachem Pristine daily, which are both bacterial supplements though not sure the difference between the two. But those or similar products can help make sure you close up any holes in your biofilter. They seem quite harmless to fish and inverts.
 

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High levels of ammonia is also toxic to beneficial bacteria! I believe that Amazonia Aquasoil must have several water changes before a cycle can begin.
That sounds very feasible, but any idea what constitutes a high enough level of ammonia for this to happen? Maybe this is why big daily water changes are recommended for the first week?

I set up 3x nano shrimp tanks over the past 6 months, all with the same Amazonia soil. On the first one I used seeded filter media from my main tank. The cycle started straight away as expected, stopped as the soil dropped the pH right down, but then started back up as soon as I added a bit of KH to bring the pH to mid-6's. So my feeling is that the "high" ammonia levels of a new Amazonia soil setup were not enough to kill the existing colonies of bacteria, but the low (<6) pH was enough to stall them. In my other tanks (with new bio-media) it seemed that the cycle wouldn't even think about starting until the pH stabilised at 6+, even with the addition of copious amounts of Seachem Seed. So for me it seems that it is the low pH that holds back the cycle, not the high levels of ammonia (or maybe it is both, but the low pH persisted for longer?)

Another thing I have just started doing to hopefully get more consistent test results, is after cleaning, do a final rinse of the API test tubes with distilled water so there isn't any tap water residue drying on them. I got one of those medical squeeze bottles with the bent straw top, filled that with distilled to final rinse off measurement equipment after cleaning. I learned that trick in a lab a long time ago, we would final rinse everything in distilled.
Good idea - I will try this too! If it is cross contamination between tests, I think it could well the the caps that are the issue rather than the tubes themselves.

I had also wondered whether using my finger to cap the tube for the shaking after adding the first drops might be the cause. But I tried using the caps (as I know you should!) and still got quirky and inconsistent results, so have now ruled this out.
 
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