Ph continues to drop

[Pilotx1]

55 gal tank, low fish load of 1 GSP, 6 regular guppies and 1 8" bala, I adopted away the tinfoil I previously had and the bala will be going after I get the water fixed since the ph in the tank is too low to safely move him out.

Over the past few weeks/months I have noticed a very slow drop in the ph of my tank on my ph controller (co2 injection for the plants) I had my ph target set at 6.5 on the controller. The problem is not with runaway co2 injection as I unplugged the solenoid from the controller yesterday and the ph continues to drop. I also suspected the probe was going bad and did the proper ph chemical test and the low reading was confirmed.

Im running a very low level brackish mix with the spec grav at 1.004 right now, and i bump it up a touch about once a month for the puffer as he gets older which is another reason the tinfoil and bala are moving out not to mention their size.

the filter is an eheim pro2 2128


what can cause a continuous PH drop. Im at a loss here....

[AngelMom]

What are your readings (actual numbers) for ammonia, nitrite, nitrate, GH and KH? Do you have live plants? If so, how often do you fertilize? Do you have driftwood in the tank? What is your maintenance routine ... how often do you do water changes (and how much is changed) and what does your filter maintenance consist of?

[Pilotx1]

What are your readings (actual numbers) for ammonia, nitrite, nitrate, GH and KH? Do you have live plants? If so, how often do you fertilize? Do you have driftwood in the tank? What is your maintenance routine ... how often do you do water changes (and how much is changed) and what does your filter maintenance consist of?

ammonia is at 0
Nitrate is about 40 mg/l
phosphate is 2 mg/l (the source of my algea)
KH is 0 to 1 Degrees/ under 17.9ppm
GH is 40 degrees, well off my chart but it has always been this way

yes I have live plants they arent doing well because of hair algea which ive had all along
fertilizing is with flourish tabs every 3 months and it due for reapplication now

I have 1 large peice of driftwood its aged however and was boiled 2 hours before it went in tank over a year ago.

water changed are every other week and are 10-15 gallons approximately.

the eheim has been in operation untouched since march its flow is still strong

[AngelMom]

Your pH has crashed because the KH is way too low. It needs to be at least 3dG (about 35-40 ppm) to be able to maintain a stable pH.

You have a couple of options here. One is to get a product like Kent's "pH Stable" and follow the directions on the jar. The other is to use plain baking soda to raise the KH, but you'll need to experiment a bit with that to find the proper dosage. Either way you'll want to go slow.

And a couple more questions ... do you by any chance use RO or DI water for your water changes? Are you adding any chemicals in an attempt to control or adjust the pH?

Also, are you adding liquid fertilizers for the plants as well as the tabs? Most plants feed through the leaves and need the liquid nutrients. It'll help your algae problem too ... I find hair algae shows up when there is too much iron and not enough potassium in the water.

Regarding the filter ... I'm assuming you don't have any carbon in there? No worries if you don't, but if you do, be aware that it needs to be changed at least every 6-8 weeks or it will leach contaminants into your tank water.

BTW, might want to have someone verify the GH ... I don't think I've ever heard of 40dG. :eek: We have really hard water and we're only at about 15 dG. If your test kit is more than a year old (or has been open for a year or more) you might want to replace it ... the reagents in most test kits have a shelf life of about a year once they are unsealed.

[Pilotx1]

Your pH has crashed because the KH is way too low. It needs to be at least 3dG (about 35-40 ppm) to be able to maintain a stable pH.

You have a couple of options here. One is to get a product like Kent's "pH Stable" and follow the directions on the jar. The other is to use plain baking soda to raise the KH, but you'll need to experiment a bit with that to find the proper dosage. Either way you'll want to go slow.

And a couple more questions ... do you by any chance use RO or DI water for your water changes? Are you adding any chemicals in an attempt to control or adjust the pH?

Also, are you adding liquid fertilizers for the plants as well as the tabs? Most plants feed through the leaves and need the liquid nutrients. It'll help your algae problem too ... I find hair algae shows up when there is too much iron and not enough potassium in the water.

Regarding the filter ... I'm assuming you don't have any carbon in there? No worries if you don't, but if you do, be aware that it needs to be changed at least every 6-8 weeks or it will leach contaminants into your tank water.

BTW, might want to have someone verify the GH ... I don't think I've ever heard of 40dG. :eek: We have really hard water and we're only at about 15 dG. If your test kit is more than a year old (or has been open for a year or more) you might want to replace it ... the reagents in most test kits have a shelf life of about a year once they are unsealed.


what can cause the KH to go to zero like it did, I have notes(not with me now) on what the numbers were when I initially started up the c02 injection and the charts for calculating the carbon content in the water for the plants

I do not use RO or DI water, it come straight from the tap(chicago suburb), gets dechlorinated, and now put in a bucket with the necessary seasalt mix to get to my desired spec gravity, it sits in the bucket for probably an hour with a small pump agitating it to make sure the salt is all dissolved

until now I have never had a PH problem, co2 injection lowered it a bit but was easily controlled, no I am not using chemicals to control the ph, Im leery to do so as well

the GH has always read that high, I even returned the test kit to the store saying it was defective and got another after I read that the first time. the kit I did the above numbers on is less than 4 months old.

iron is very likely high in my tank, the gravel bed is 100% flourite, phosphates are high as well. i discontinued the liquid ferts over the summer trying to get rid of the algea, prior to that I had been using flourish, and 2 others which I cannot recall the name of but I bought them to try since they didnt have phosphate

for the filter Im running the standard ehein setup with the ceramic tubes, coarse and fine pads and the gravely looking stuff, no carbon. I got away from carbon when I got the eheim to replace my magnum and have loved every minute of it

[AngelMom]

what can cause the KH to go to zero like it did, I have notes(not with me now) on what the numbers were when I initially started up the c02 injection and the charts for calculating the carbon content in the water for the plantsUsually it's from using RO/DI water without adding replacement minerals, but since you've confirmed you don't use RO/DI it's possible your tap water is the cause. Any source of acid will reduce the KH (this is how the chemicals that lower the pH work ... they are a weak acid solution). If they aren't getting enough carbon, plants can lower the KH as can driftwood or filtering with peat (though all these are very slow as far as the reduction rate). Have you tested the water out of your tap? If the KH of the tap water is low to begin with, it will have little effect on the tank.


the GH has always read that high, I even returned the test kit to the store saying it was defective and got another after I read that the first time. the kit I did the above numbers on is less than 4 months old. Weird. Not sure what else to say except that if the fish seem fine with it I wouldn't worry about it too much.


iron is very likely high in my tank, the gravel bed is 100% flourite, phosphates are high as well. i discontinued the liquid ferts over the summer trying to get rid of the algea, prior to that I had been using flourish, and 2 others which I cannot recall the name of but I bought them to try since they didnt have phosphate There is a link in my signature regarding algae in planted tanks ... check the website out, he has loads of useful information there. One thing that I wasn't aware of when I started keeping live plants is that the plants will grow (and use the nutrients up) as long as all the compounds they need are available. But once the least abundant compound has been used up, they stop feeding and the other compounds are available for the algae to use. It seems a tad backwards, but you can actually tell what compounds are missing by the algae type you're getting. Ideally (when the plants are feeding all the time) you will only see small amounts of the green-spot algae.I've managed (over a couple of years) to get very close to that in 3 of my tanks and only need to scrape the front of the tanks every 3 months or so ... still working on the other 2 tanks. :rolleyes:


for the filter Im running the standard ehein setup with the ceramic tubes, coarse and fine pads and the gravely looking stuff, no carbon. I got away from carbon when I got the eheim to replace my magnum and have loved every minute of it Cool ... I never run carbon either unless I have had to medicate for some reason and want to pull the residual meds out of the water. Gotta ask the questions though. ;)

[Pilotx1]

Usually it's from using RO/DI water without adding replacement minerals, but since you've confirmed you don't use RO/DI it's possible your tap water is the cause. Any source of acid will reduce the KH (this is how the chemicals that lower the pH work ... they are a weak acid solution). If they aren't getting enough carbon, plants can lower the KH as can driftwood or filtering with peat (though all these are very slow as far as the reduction rate). Have you tested the water out of your tap? If the KH of the tap water is low to begin with, it will have little effect on the tank

Weird. Not sure what else to say except that if the fish seem fine with it I wouldn't worry about it too much.

There is a link in my signature regarding algae in planted tanks ... check the website out, he has loads of useful information there. One thing that I wasn't aware of when I started keeping live plants is that the plants will grow (and use the nutrients up) as long as all the compounds they need are available. But once the least abundant compound has been used up, they stop feeding and the other compounds are available for the algae to use. It seems a tad backwards, but you can actually tell what compounds are missing by the algae type you're getting. Ideally (when the plants are feeding all the time) you will only see small amounts of the green-spot algae.I've managed (over a couple of years) to get very close to that in 3 of my tanks and only need to scrape the front of the tanks every 3 months or so ... still working on the other 2 tanks. :rolleyes:

Cool ... I never run carbon either unless I have had to medicate for some reason and want to pull the residual meds out of the water. Gotta ask the questions though. ;)

Ill check KH tonight from the tap

Its been suggested to me that I add come crushed coral/ seashells to the tank to help with the PH. it would help bring up the KH as well no?

before I ditched the magnum I discontinued carbon use at the suggestion of one of the guys at the LFS as his theory was that it was stripping my ferts from the water and hampering the plants


Ive read adn tried a large number of things regarding the algea and havent yet been able to find the balance for good plant growth and low algea,
one thing I have noticed is that the algea seems to be dying back lately(maybe it doesnt like the ph) and the plants have just recently shot up some new leaves. prior to going to love plants I never really had algea problems but when I did i went full system with dual t5ho lighting on a timer and co2 injection via controller, as well as the flourite substrate.

[Pilotx1]

from the tap KH is 6 deg 107.4ppm

[AngelMom]

Cool, so at least your tap water is alright (relatively speaking ;) ). Honestly, if it were me, I'd correct the immediate problem and keep a closer eye on things for a bit.

I would not add any crushed coral or shells ... they won't raise the KH or pH much unless you add a lot, but they will raise the GH and that's already high enough. :p

I don't like using carbon with adding ferts either, but my LFS owner swears his wife (who does some gorgeous planted tanks) runs carbon in her filters. My personal opinion is that even if there aren't live plants in the tank, carbon isn't needed as long as there is adequate flow, a good bacterial colony in the biological bed, and regular water changes are made.

Not quite sure what else to tell you at this point. If you think of anything else that might be connected (like the CO2 maybe went haywire a bit ago?) definitely let us know. Maybe someone else will think of something else in the meantime.

The laterite/Flourite is probably contributing to the algae problem. The only tanks I've ever gotten hair algae in have all had laterite mixed with gravel as a substrate. And honestly? I see absolutely no difference in the plant growth in the tanks with just gravel as a substrate. I suspect that some of the more sensitive root feeders (like some of the more exotic swords that can be finicky) might do better with the laterite but I don't have any experience with them.

[Pilotx1]

Ive checked over the c02 system and theres nothing wrong with it, I built it peice by peice rather than buying a kit.

the solenoid valve I am using is for industrial automation and have a mtbf of 1million cycles
the regulator is a dual stage with its low pressure side sprung for at most 15 lbs output and is gauged to 20psi.


the baking soda is what you recommended to bring the ph back in line will it also boost my KH and wont the sodium affect my spec gravity

[Pilotx1]

I put just under 1 tablespoon of baking soda into the tank, and it brought the PH up almost immediately to 7 which is not how i wanted to do it.

the c02 injection is back online to prevent the PH from spiking past 7

the KH also measures 7 degrees now.

[AngelMom]

Yeah, it will do that ... which is why I said ".... you'll need to experiment a bit with that to find the proper dosage". Just arbitrarily dumping some baking soda in without determining how much should actually be added can bring about additional problems, as you've seen. The baking soda does not directly affect the pH, it only raises the KH ... it is the reaction between the KH and CO2 that determine the pH.

Also, I wasn't implying there was a problem with your CO2 system, merely using that as an example of things that could be considered in an attempt to figure out why your KH dropped in the first place.