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Tap Water Spike

Pixel Shark

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Pixel Shark



First time visitor to the forums looking for some advice and guidance on a new issue of mine. 

Bit of a backstory - I’ve cared for fish when I was a teenager and decided to get back into the hobby last year as an adult. I’ll admit I was perhaps a little over confident in my skills, but was excited to start fish keeping again.


I currently have two aquariums: a 20 gal tall and a 6 gal cube. Both are heated at 78 degrees with live plants. The 6 gal has a single female betta. The 20 had six neons, a khuli loach, and a female betta before complete chaos.


Last Sunday, I decided the 20 gal was due for a water change (I normally do water changes once a week) between 25-40%. Didn’t think much of it since the past year, I haven’t had any tap water issues other than a pH of 7.8 and my fish didn’t seem to mind. 

The following day I woke up and found two neons dead and my betta stressed and not looking well. I did a water test and found there was a small ammonia spike and the pH was suddenly at 8.4. I decided to do another water change hoping these would drop, but I continued to have a spike in both and lost the betta and another neon in those few days. I spent countless hours searching Google for answers and mostly got the “keep doing water changes” feedback. No success.

Today I decided I was going to change from gravel to aquasoil to see if that could help lower the pH. I also changed out my natural rocks to rocks that wouldn’t change my pH just in case. I knew this would mess with any kind of aquarium balance so my remaining fish are in a temporary tank filled with the old water, aeration, and heater so the tank can “restart” sort to speak. Once the tank was beginning to cycle (and I was done rearranging plants) I also did a a quick 30% change on my 6 gal. Afterwards I did a water test on both aquariums to make sure everything was okay.


pH was suddenly off the charts even with the liquid high pH test (8.8). There was also an ammonia spike from the usual 0 ppm to .25-.50. The ammonia was understandable with the 20 gal now that I disrupted the cycle but my 6 is cycled and previous tests were always 0 ppm. 

I quickly took my lone betta out of her tank and put her in the temp tank with everyone else so now both my main tanks are empty.


I ended up getting pH down (not my preferred method to lowering pH) and was able to lower the pH to 7.4 (tanks have no fish still). On a whim, I tested the tap water and found the exact same results as my tanks when just a few weeks ago, the results were very tank friendly. There’s a lot of mentions that water companies occasionally tweak how they condition the water and how it impacts aquariums and I have a sneaking suspicion this could be the case. Has anyone else experienced such extreme fluctuations before? If so, any advice on how to combat it? I’m afraid I’ll have to start buying distilled water for weekly water changes…

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Before you jump to conclusions, you should test your tap water AND (assuming you see the same issue in those tests) call your water company to ask about this. 👍


(If you don't see the issue when you test your tap water, then there may be something else at work here.  See below...but there are other potentialities.)



It's worth pointing out that it is always risky upsetting the balance of a freshwater tank (maybe any tank) that has been un-maintained for an extended period.  A more measured approach to the situation in the first place may have prevented most of the side effects and should have given you more of a chance to react before things "went off the rails".  You did about everything right in your reaction tho!  👍


FYI... If you look up a pH-Temperature-Ammonia chart to convert the number your test kit gives you (total ammonia, NH4) to tell you the amount of that ammonia that would be toxic ammonia (NH3) in your tank, you'd see a multiplier of .1950.   If we assume your ammonia was in the middle of the range you stated (which gives us 0.38 ppm NH4) then that multiplier indicates that there would be about (0.38*0.1950=). 0.074 ppm NH3.  You can run the same calculation for your other pH spike.  Anything around or over 0.05 ppm NH3 is usually considered to be "entering the danger zone" where you start doing water changes and/or detoxifying the ammonia by external/chemical means.  (1.0 ppm is considered a lethal "dose" of NH3.). A good read.


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Pixel Shark

Thank you for such a swift reply!


I went ahead and did another test on my tap water just to confirm and Ammonia was sitting at 1.0 ppm, pH 8.8 or more. Even Nitrate is suddenly showing on my tap water with a 5-10 ppm. The 20 gal shows that as well, but understandable since I did almost a 80% change to redecorate/reset. My 6 gal which only got a 30% water change like every week is sitting at an Ammonia of .25 ppm and Nitrate is at 5.0 ppm. It's frustrating because I even noted an odd smell coming from the tap (like wet rock or soil), but didn't even think the composition had changed last week.


As an update with pH Down since I dosed before bed last night and was receiving test results of 7.4... it is now back up to 8.0. MUCH better than the 8.8+ it was testing before, but I'm concerned it's just going to keep climbing right back to where it was.


I went on an excursion to try and find distilled water just to try and correct the issue, but either all three grocery stores in the area are sold out or temporarily stopped selling it. I'm at a loss at this point on how to proceed. 

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Pixel Shark

As an additional update! I went into some heavy duty digging down the forum/reddit rabbit hole for answers.


Apparently cities commonly in the spring time make adjustments to the chemical make up of tap water to anticipate the warmer (evaporating) summer season. Since I only just bought the aquariums at the end of last May, I missed this sudden spike. I guess this is a very normal, city response from the water company - the more you know!


I am heading to the store to get spring water to fix up the tanks - not distilled as I don't have a way to add the lost minerals. A lot of responses within forums suggested ensuring the tanks are well planted to minimize water changes during this period of time until the tap water stabilizes again. Until then, invest in spring water gallons to refill as needed! This is the first time I've ever lived and owned aquariums so close to a city. I've solely relied on well water in the past and my angels loved it so never imagined tap would be any different. Now I know that I'm not going crazy and it's been my tap water all along!

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Pixel Shark

Final update to my crazy aquarium thread story:


Just wrapped up stabilizing the aquarium with spring water. I tested the spring water before adding: pH 8.0 and 0 ppm Ammonia! Nitrates were a little higher than I expected (30 ppm), but both tanks are heavily planted so I anticipate this will correct as the tanks readjust.


MCARROLL - Thank you so so much for your response. It was the little jump start I needed to start rethinking the problem! I was borderline in tears; my fish are my babies and watching them suffer/die has made a very stressful week. I was staying up until 1 am tending to water changes and water tests! My little betta (6 gal resident) is so so precious to me that I'm hoping this weekend's insanity will be all in the past and I can continue enjoying her fierce personality.


So far, I've now added peat moss, aquasoil, and almond leaves to help combat any pH fluctuations and while stopping for spring water, I also treated myself to some additional live plants to encourage aquarium health. Lesson very much learned: don't ever trust tap water 100%!

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On 4/7/2024 at 10:56 AM, Pixel Shark said:

Apparently cities commonly in the spring time make adjustments to the chemical make up of tap water to anticipate the warmer (evaporating) summer season. Since I only just bought the aquariums at the end of last May, I missed this sudden spike. I guess this is a very normal, city response from the water company - the more you know!

Yes!!   Like I already said, you should actually call your water company and ask them about it – especially now that you have confirmed your test results on a fresh tap water sample.  


While they do make seasonal changes, to me it seems unlikely that you're getting the water quality that they intended....so what you have so far is not an answer, it's just confirmation on who to call to find out the details and maybe get it corrected.  👍


The folks at every water company I've had to deal with were really helpful and friendly – more than a few times they even into aquariums themselves.  


Remember that even as true as it is that they make seasonal changes like this, it's just as possible that something isn't right on their end (or something exceptional happened on their end) and you really should let them know about it.  


What they do is more of a balancing act than a cut-and-dried science – so there's room for things to vary from "what should happen" in some instances.  Usually they can tweak things to make a better balance – they just have to know there's an issue.  


On 4/7/2024 at 2:24 PM, Pixel Shark said:

Lesson very much learned: don't ever trust tap water 100%!

The real lesson isn't to fear tap water – it's to KNOW your tap water...which also means knowing YOUR water company and its habits.  (Thankfully they're just a phone call away!)

Water companies always post water test results, so lots of trends can be picked up just from looking at a few years worth of water reports.


But IMO, talking to someone there about your current situation is worthwhile.  Let us know if you give them a call!  🙂 





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