Ph dropping significantly

Hey all,

We're beginning to run into a new problem. Over the past several weeks our ph has been slowly dropping, to where now it's about 6.8. A few weeks ago it was holding steady at about 7.6-7.8. I know that our fish prefer the lower ph so it isn't an issue at the moment, but we don't know what's causing it to drop and how far it's going to go. I don't want it to drop too far below 6.6 or so. I've included our water parameter chart that we've been keeping so you can see our levels and fluctuations. (If you haven't read my other posts, we added fish a little too early and are still in the last stages of the cycle, that is why the high nitrite readings. We're doing water changes every 2-3 days and dousing with Prime a couple of times a day.)



What we have in our tank:

Inert gravel substrate
One medium sized piece of driftwood (~12in high x~6-7in wide)
One medium sized lava stone (~10in high x ~6in wide)
Two halves of a ship decoration
Three fake plants
Two Anubias plants
Four moss balls

6 Blue Moscow Guppies with about 15-20 fry
2 Bristlenose Plecos
3 Yoyo Loaches

Does anyone know if any of the decorations we have would bring down the ph? Right now I'm looking at the driftwood and the plants as the culprit, or is it just a natural part of the cycle for the ph to go down? Also if it keeps going down, what can we do to get it back to 6.5-7?

Yes, remove the driftwood as it will lower it. Are you testing at the same time each day as PH fluctuates during the day.

The pH is closely connected to the GH, KH and level of CO2 dissolved in the water. So first off, can you give us the GH (general or total hardness) and KH (carbonate hardness also termed Alkalinity) for your source (tap) water? If you don't already know these, you may be able to get them from your municipal water authority, on their website or by calling them. We need the number and their unit of measurement (there are several). Once we know these, it will be easier to explain the pH.

Another point, when you test pH of your tap water, you need to out-gas the CO2 (levels vary, depending). This can be done by letting a glass of fresh tap water sit for 24 hours before testing. Sometimes you can also agitate very briskly a small amount of fresh tap water, then test. This is not necessary with aquarium tank water, just tap water.

Third point, you should check if your municipal water authority adds anything to the water to raise pH. This is good to know either way. But some authorities do this to prevent corrosion from more acidic water, and the effect is frequently temporary (depending what they use) and the pH will thus lower in the aquarium.

In every aquarium there is a natural biological process that acidifies the water and thus lowers pH, so this is not unusual. But the extent to which this occurs depends upon the above items, so we need to know those in order to sort this out.

I generally test the water some time in the evening, but it isn't the exact same time every day, usually in a window of 3-4 hours. I actually have a gh/kh kit coming in the mail today, I could not for the life of me find the alkalinity, but what I could find online from the city was:

Hardness mg/L: 115-128
Hardness Grains per gallon: 7-7.6


The chemicals used at the Water Treatment Plant during the reporting period were:


aluminum chlorohydrate (ACH) – a coagulant to aid tiny particles in the water to join together to


form larger particles that are easier to settle and/or filter out

citric acid and sulphuric acid – used to clean the membrane filters

sodium hydroxide – used to neutralize the spent membrane cleaning solution

hydrofluorosilicic acid – used to optimally fluoridate the water to prevent tooth decay

hydrogen peroxide – used in the UV advanced oxidation process to destroy taste and odour


compounds

polymer – used in the wastewater stream to settle out solids

sodium hypochlorite – used to control mussel growth in the raw water structures, to disinfect the


water, and also to clean the membrane filters

sodium bisulphite – used to quench excess chlorine

This is beginning to make sense. First on the GH and KH. The hobby uses two scales, dH (degrees) and ppm (parts per million). To avoid lengthy explanations, for our purposes we can take 1 grain per gallon as equivalent to 1 dH. And mg/l is the same as ppm. [1 dH is 17.9 ppm so you can change degrees and ppm back and forth by multiplying or dividing with 17.9]. Your GH at 115-128 ppm [= 6 to 7 dH] is soft water. The KH at 7 to 7.6 grains per gallon equals 7 dKH.

The GH and KH serve to buffer pH, and when these numbers are low as here the buffering is limited. So the natural organic process in the aquarium (decomposition of organics by bacteria) will acidify the water and the pH will lower. This is natural and not a problem provided you have soft water species that are suited.

Attempts to raise the pH would have to take into account the GH/KH and this is quite complex. It is much easier (it makes water changes less convoluted for one thing) to select fish suited to your water parameters. Loaches and Bristlenose are soft water fish; guppies are not. Avoid all livebearers (guppies, platies, mollies, swordtails, Endlers) as they need harder water to be healthy. Soft water fish include the tetras, rasbora, danios, barbs, most catfish like cories, loaches, gourami, and some others. This is very general.

I won't get into all their additives, this is way beyond my chemistry. The above explains the pH lowering which was your initial question.

Is there any way to know how low it may go? Or if and when it'll even out? Our tap water is ph 7.7, so water changes raise it a bit. I'm thinking that you are right though, that the soft water is contributing to the alkalinity causing the ph to drop. We're mainly just worried how low it will go and where it will end up.

Aynia said:

Is there any way to know how low it may go? Or if and when it'll even out? Our tap water is ph 7.7, so water changes raise it a bit. I'm thinking that you are right though, that the soft water is contributing to the alkalinity causing the ph to drop. We're mainly just worried how low it will go and where it will end up.

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The only way to know is to let it do what it does and see where it ends. I have/had 8 tanks, all very soft water, and the pH varied depending upon the individual tank's biological system. Some tanks remained around 6 for years, others remained below 5 for years. My tap water is pH 7 due to the soda ash they add, and this has had no impact for over a decade now.

As @Byron says the guppies will always struggle in your water. One of my softwater tanks has a pH below 6 (that's as low as my test goes), the other is about 6.6, even though they get exactly the same water. Doing a weekly water change of at least 50% (more is better) will keep it stable. I don't worry about the actual number.

ONE OF MY RANTS - sorry skip if you want to!!

I too have experienced lower PH over time. Our city's avg PH is 9.4 ppm and goes as high as 9.99 ppm. That's the truth - no freshwater fish I know of can handle those PH levels - they are even too high for Salt water/Reefs. So what am I to do? Just give up on fishkeeping because my PH "is too complex" or just go for it and add either PH up or PHdown. I've been successfully doing this for over 6 months with NO fish deaths. I can hit 7.0 from a PH of 8.9 (highest my kit goes) usually over 2-3 days, never giving massive doses.

But fish really can tolerate far more than some of us think they can - (like my pour Gourami that hasn't eaten for 4 weeks due to fish bladder disease and she hates peas and nobody will offer me ANY help - (so I'm prepared to euthanize even though she really looks perfectly OK. just a little thin - or I may not euthanize since if I didn't know she had bladder disease I would never have noticed that she hasn't eaten in 4 weeks) She also dispelled the so called "FACT" that Gourami's MUST take a breath of air ever so often - over a period of intense 2 week observation she NEVER went up for air and she DIDN'T DIE now that I have her in a small short tank I gently lift her up to breathe - which she does then she'll float around for about an hour breathing until she falls back down to the bottom and we start all over. She goes all night without taking a breath - as I suspect all the other Gourami do when they sleep.

When I add PHdown after a large water change I slowly lower it to 6.8-7.2. Then it sometimes holds there for the longest time, or slowly drops to 6.0 during the week which won't work - so I PHup it (much smaller dose) to about 7.0 I have to do this after every weekly water change since my water changes make PH rise to an uninhabitable level and then after treating drops too low. - but if it was terribly toxic my fish would die as soon as I did a water change because it may take me an hour or more to decide how best to adjust the PH and they are floating in an 8.9+ PH during that time.

So what I have done is throw out my thoughts on GH and KH because they are hard to treat compared to PH.

GH=10.6 (range of 6.1-15.8)
KH=5.3 (range of 2.6-7.7)
PH=9.4 (range of 8.5-9.9)
(for some strange reason my water is typically at the low end of GH and the middle of KH)

My point is we can't make assumptions that something can't be done because it's not in the books somewhere or doesn't work out mathematically. When I look at the muddiness of fresh water and think that most of these fish came from that mess it makes me wonder why anybody worries about cloudy water (I do know the real reason we worry and why we should worry) but even some owner's water can get really cloudy, nasty and messy and for some reason their fish hang on amazingly well. In my opinion, fish, like humans are really very adaptable and tough. I say that because by now with all my horrible mistakes I should have killed all my fish three time over and other than new purchases and one serial killer danio I've have only had 1 death (I accidentally dropped a lid on him as he tried to escape the net)

Maybe like every other newbie I have a god looking over us idiots.

So we got the GH tester yesterday, and it's reading a GH of 314ppm. Unless I'm wrong, that translates into a GH of 17.5 degrees!!

Could this have been part of why we lost the three loaches? There's just so much going on with this tank at the moment it's hard to keep track of what could be affecting the fish.

That is a lot harder than you found on-line in post #4.

Can I ask, what type of tester have you got, and what brand?

Ok that sounds very different. 314ppm is extremely hard water and not suitable for loaches, tetras, corydoras and many other soft water species. Guppies and other livebearers will be fine. I only keep softwater fish so others will need to advise what other fish are suitable.

It is outside the range for bristlenoses. My own 15 year old BN spent the first 12 years of his life in very hard water so hopefully these will be ok.

It may be worth double checking your results. That seems like a massive jump from what your water company says. It is also worth testing your tap water. It may be that your gravel is not inert after all. GH does not change significantly over time so you can test a glass straight out of the tap.

https://www.amazon.ca/dp/B07MZ47MGC/?tag=

This is the water tester that I got off Amazon. When I test the water from the tap it flashes red and says 314ppm.

I have never used that type of tester so I have no idea how reliable they are. I used the API liquid GH tester (and KH, as they came in a pack together)

But considering the huge difference between this tester and the values you found on-line, I would take some tap water to a fish store and ask them to test for GH, and go with whichever two values are closest and ignore the one that's way different.

Aynia said:

This is the water tester that I got off Amazon. When I test the water from the tap it flashes red and says 314ppm.

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That tests TDS (total dissolved solids). There really is no way of knowing what that is made up of. GH and KH typically only need to be tested once. So it may be worth using the 6 in one strips. A lot of people will tell you they are inaccurate but TBH they are good enough, and if the values are anywhere close to what your water company says that's good enough.

Until we know for sure it may be best not to buy any more fish, and I would stick with the published data unless your tests show otherwise.