My pH is low while cycling. Should I do anything?

[Arwen Vaughan]

I am fishless cycling a 150 gallon IBC tote with ammonia. It is day 7 and no traces of nitrite or nitrate. In the last few days the pH started dropping and is now at 6.2. I am trying to take the advice I keep hearing to do nothing and just be patient. So, I am asking for advice before adding anything. I guess there are no fish, plants, or bacteria yet, so...hang tight or add something? I bought a little calcium carbonate and potassium bicarbonate in case I need it. What do you think? 

[Vlad Jovanovic]

Hi Arwen, 7 days is a normally not enough time to start seeing registered NO2, NO3 values, so don't fret on that end...

But a pH of 6.2 is not so great for a system that has yet begun to establish a bacterial colony IMO. Once they are thriving and doing their thing, sure. But at this point you would be doing them a favor by raising it a but. (I'm not saying they cannot become established...just that they will have a much rougher time of it...longer too).

But BEFORE you do that, do yourself a favor and go to the pet store and purchase a kH (carbonate hardness) test kit. It should cost just a few dollars, but is a wonderful tool to have that will help you to get a handle on what kind of source water you are dealing with. It is not a necessity, but you may later come to appreciate it's value.

I'm betting that your kH is also really low as well. Below a certain degree of carbonate alkalinity, existing already established bacteria cannot live, (regardless of pH) let alone get a foothold and build a colony in a new system. So it's nice to know those values.

If you don't care so much about knowing what is going on in your system, with your water and why... etc...and just want a short answer then mine would be: Use a combination of the KHCO3 and CaCO3 that you have already bought to raise pH value to between 7.6 to 8.2 ...

[Arwen Vaughan]

Wow, thanks for the feedback!! I looked at the water quality report for Denver City water and it looks like the hardness varies from between 45 and 115 ml/L (or 2 an 7 g/g). I don't know if that tells you anything. I'll get a test kit later today so I know more precisely. This is Denver municipal water, not well water or anything like that. So, would you say that the kH is probably just low because it is city water?

I know it is tough to say, but do you have any rough guide on the amount of KHCO3 or CaCO3 to add for a 150 gallon tank. Should I start with a teaspoon and wait a day, then repeat if necessary? I am very patient so whatever it takes. :)

[Vlad Jovanovic]

Not because it's city water...just because of where that particular city gets its water from :) Different cities will have different types of water issues depending on their location on the planet...anywho's...

At 45 mg/ L that would be real baaad for trying to establish bacterial colony...whereas 60, 80, 115 (or above) mg/ L would be much, much better. Mine started out at over 300 mg/ L (afer testing it today it's at about 80 give or take). Measure the kH of the water currently in your system and see where your at (since what Denver Muni lists is a pretty wide possible range...kH of a cities water supply or  well water, will change with the seasons...after the rainy season/melted snows it'll bee lower, during /after times of drought or summer it tends to be higher etc...).

Carbonates/bicarbonates are pretty forgiving (not so with hydroxides). But I'm still pretty loathe to give you direct amount to add to your particular system...and with out that kH test you will only be able to monitor effects on pH...Which is all most people do anyways. You will not be able to raise your pH with those carbonates to more than 8.3 or so no matter how much you pour in...so aim for just under 8 (7.6 should be fine and gives you leeway should you over shoot things...Whatever you do, just don't stress about it. Since nothing you can do is really going to be able to harm anything and/or is easily remedied). 

Here's a fun bit...add a table spoon of each then measure pH in a couple of hours (say 3 or 4 hours). Take notes. Keep doing that until your pH is between 7.5 and 8. That should (very roughly) bring your kH into the neighborhood of between 80 and 120...kH is important because it is the inorganic carbon species food source that your bacteria need, and you need to have enough of it, while "too much" isn't really a big problem (except for it will keep your pH high...but this isn't really even a problem unless you have lots of plants...which you don't...so that'll come later...) Take a look at my photos...all that you see in the GH was grown with a pH between 7.5 and 8.3 (and most of it until very recently, was closer to the pH 8.3) with a 'very' high kH (started out at over 300+ and has been slowly falling over the past few months mostly due to bacterial respiration and a tiny bit of intervention on my part to help them out with that a bit)...

Of course I cycled with humonia instead of janitorial ammonia, so there is a much, much, much higher level of different plant essential elements present in solution than if I had used store bought ammonia (which will provide only nitrates). I think this is part of why my plants can deal with the higher pH levels without experiencing pH related nutrient lock-out issues that many such new systems are prone to. That and I was realistic with what I planted at first. Lettuce and greens instead of cucumbers and toms...they will come later...

You are probably not cycling that way, so shooting for a pH of just under 8 (and hence a kH of around 100 give or take) is probably a better bet for you in your particular situation.

Take it slow and takes notes (since without knowing your kH and some other stuff, it's difficult for anyone to give you a decent or reliable answer, and besides it will be more meaningful for you to do it yourself. Again, it will be impossible for you to mess anything up in any meaningful way (at this point), so have fun with it/learn and don't stress.

[Arwen Vaughan]

Thanks you again for the information. I am learning so much right now and really enjoying it. I bought some test strips that include hardness, and it looks like almost 0 carbonate in the water! I got some seaweed extract and chelated iron powder (from HEDTA) as well. So, I was going to alternate adding the KHCO3 and CaCO3 like you suggest and also add a little bit of seaweed and iron as well so I can start the plants off soon. Sound like a good way to go?

But here is what the test strip says...

General Hardness = 180

Carbonate Hardness = 0

pH = 6.0

Ammonia = 2.5

Nitrite = 0

Nitrate = 0

[Vlad Jovanovic]

Just a heads up on test strips...The ones I've ever used for anything thus far have all given pretty unreliable results. The liquid drop tests are the way to go IMO. Anyways...

Yeah, get that kH and pH up...but you don't have to wait to get your seeds started at all. Heck, they will grow for a good long while just fine with tap water and candlelight! The cotyledons (those odd shaped first leaves that emerge) contain all the nutrients and energy the plant needs until about the time the second set of true leaves begin to emerge. So there is really no reason to wait at all. Besides, most plants can do just fine up-taking ammonia as an N source particularly in early vegetative phases of their lives (this changes later on for flowering and fruiting, where N in the form of nitrates becomes much more important, and ammonia can start to have various deleterious affects...but for the short term future, you'll be just fine)...So get those seeds started

[Vlad Jovanovic]

One other thing Arwen...does it say anywhere on your kH test strips what scale they are using? Most often (even in the States) the old German dH (degrees of hardness) scale is used, or ppm (there are some other goofy ones sometimes used in the US, but the two I mentioned appear to be most popular...Though I'm not really in a position to say since I do not live there:) I'm just riding on what some of my friends in the US have encountered...I'm thinking of Jon Parr and Benjamin, who both live in the States. I don't really know of any other people besides Jon who actually test for and understand what kH is...Not that they might not be out there, just that I've not come across them or their posts) Both of their kH test kits use the dH scale I believe.

In case it is easier for you to work in ppm (which is exactly the same as mg/ L):

1 dH = 17.8ppm

With what you've written...it should roughly take about 50 grams of those carbonates you listed to get your water to about 90ppm kH. 

But you will learn more by adding a little, then testing pH and kH taking notes...and getting a chance to observe how the two are related.

AND JUST TO MAKE SURE...You do have CaCO3 AND NOT the Ca(OH)2 (hydrated lime) that you asked about in the chatroom the other day...right? Because hydroxides are a different beast  than the carbonate altogether...

[jim mckee]

Arwen

How much of your system is set up?

To me- one should cycle an aquaponcs system with grow beds and all the associated mishmash in place because the Bactria that is attracted and fed ammonia and a few more microgoodies (I like making up fake words) touch stick and live on all those surfaces. More area = more bacteria magnet. And that's if your using sterile material, so  if all you are cycling is 150gl IBC you just got water in a bucket.  Meaning only the square area exposed to the air is all you have to attract the bacterias.

I like starting a system with some natural material like creek gravel (even a 5gl bucket of creek rock works).  Those items  have the bacterias on them.

Hope you can use some of that.

But my system still has weeds ( I put these in for a joke and to start conversation,, dang they love the water)

[Eric Warwick]

I'm not sure what your buffering capacity is, but a sudden drop in pH like that says to me that it is very low. Buffering capacity is the amount of stable pH you have before a buffering substance runs out. Buffers are really freaking complicated, so I won't explain here. However, I will tell you the best (cheapest) buffer: carbonate (CO3). 

The best way you can get this is through NH4CO3 (ammonium carbonate)--at this stage of cycling. This takes care of the ammonium (which produces ammonia or NH3) and the CO3. Later you'll want to switch to calcium carbonate. I would do a titration to test buffering capacity once you are up and running to get a rough idea of if you are reaching an end of buffering capacity--in which case you add more. Do this maybe once a week. You don't need to have expensive lab equipment either, just a strong acid (such as hydrochloric acid), but at a very LOW concentration, for safety, a pH testing kit, and a good eye.

Look up titrations for more info' 'cause my keyboard is broken, and I've been typing this with the "onscreen keyboard".

[Arwen Vaughan]

Vlad,

Looks like all the tests on the test strips are in ppm (mg / L). I have a liquid test kit that I use for everything except the hardness. I bought the test strips just for hardness because of your advice. I'm glad I did too. kH looked like it was 0.

So, I added just one tsp of KHCO3 and 1 tsp of CaCO3 to my 150 gallon system. Three hours later the pH had come up from 6.0 to 6.8, so I just stopped. That is the pH I was thinking to shoot for. I also added a little splash of seaweed extract and 1/2 tsp of chelated iron (10% powder from HEDTA). Once the pH was up, I then added a 1 oz container of that fish tank bacteria starter stuff for good measure. Now I am going to lock the closet and just be patient.

Vlad Jovanovic said:

One other thing Arwen...does it say anywhere on your kH test strips what scale they are using? Most often (even in the States) the old German dH (degrees of hardness) scale is used, or ppm (there are some other goofy ones sometimes used in the US, but the two I mentioned appear to be most popular...Though I'm not really in a position to say since I do not live there:) I'm just riding on what some of my friends in the US have encountered...I'm thinking of Jon Parr and Benjamin, who both live in the States. I don't really know of any other people besides Jon who actually test for and understand what kH is...Not that they might not be out there, just that I've not come across them or their posts) Both of their kH test kits use the dH scale I believe.

In case it is easier for you to work in ppm (which is exactly the same as mg/ L):

1 dH = 17.8ppm

With what you've written...it should roughly take about 50 grams of those carbonates you listed to get your water to about 90ppm kH. 

But you will learn more by adding a little, then testing pH and kH taking notes...and getting a chance to observe how the two are related.

AND JUST TO MAKE SURE...You do have CaCO3 AND NOT the Ca(OH)2 (hydrated lime) that you asked about in the chatroom the other day...right? Because hydroxides are a different beast  than the carbonate altogether...

[Arwen Vaughan]

Vlad,

I also went ahead and added some small plants and seeds as well. Here are a couple of pictures. I am just going to follow your advice and alternate adding KHCO3 and CaCO3 if the pH drops to get a nice buffer going, while adding a bit more ammonia to get the cycling going. I added bacteria so that should help. Here are the pictures...

[Arwen Vaughan]

Thanks for the advice too Eric. I'll look up titration (haven't done those since college chemistry. I agree with you and Vlad that my water has very little buffering capacity if the pH drops so quick after adding just a couple tsp of ammonia.

Thanks again guys....my head is full for the day. I'll keep this post going though with my water chemistry over the next few days so the post may be helpful for someone else doing cycling. Thanks again for all the posts Vlad.

Eric Warwick said:

I'm not sure what your buffering capacity is, but a sudden drop in pH like that says to me that it is very low. Buffering capacity is the amount of stable pH you have before a buffering substance runs out. Buffers are really freaking complicated, so I won't explain here. However, I will tell you the best (cheapest) buffer: carbonate (CO3). 

The best way you can get this is through NH4CO3 (ammonium carbonate)--at this stage of cycling. This takes care of the ammonium (which produces ammonia or NH3) and the CO3. Later you'll want to switch to calcium carbonate. I would do a titration to test buffering capacity once you are up and running to get a rough idea of if you are reaching an end of buffering capacity--in which case you add more. Do this maybe once a week. You don't need to have expensive lab equipment either, just a strong acid (such as hydrochloric acid), but at a very LOW concentration, for safety, a pH testing kit, and a good eye.

Look up titrations for more info' 'cause my keyboard is broken, and I've been typing this with the "onscreen keyboard".

[Vlad Jovanovic]

Hi there Eric! Nice to see you around again. Arwens buffering capacity is apparently very low (according to his test strips...whose 'exact' accuracy I'm a little weary of, but still, it is probably next to nothing). Now Arwen could do a titration test, and while that might be a cakewalk for you Eric, it may be a little daunting for Arwen at this stage of his aquaponic journey :)  A good kH test will give him the same information really and is much simpler.

Arwen, FYI...the terms "buffering capacity", "alkalinity", "kH" all refer to the same thing and are in this case pretty much interchangeable. And it's not that difficult to understand really.

"Buffering capacity" like the term "alkalinity" refers to your waters ability to neutralize acids. That's really it. That's all there is to it (sort of). See, ammonia oxidizing bacteria create acid (carbonic acid...which is just what carbon dioxide is called when it's dissolved in water. This acid needs to be neutralized (by some sort of base) because no person, animal, nor bacteria can live in it's own waste. If it is not neutralized the pH falls so low that your bugs will not be able to function and they will die.

Now this base does NOT have to be in the form of carbonates, but in your case (no bacterial colony already established, and no kH to speak of) carbonates would be a wise choice. You see, other than neutralizing the by-products of bacterial respiration, carbonate alkalinity provides a convenient inorganic carbon food source that the bacteria need to live. A certain level of this inorganic carbon food source is needed. You are below that level. Below about kH 40ppm, ammonia oxidizing bacteria cannot do there thing regardless of a nice high pH...Hence the kH test. Keep your kH above 40ppm and all will be well. Your pH is also way to low to facilitate cycling.

Remember kH (carbonate hardness) is just a measure of carbonate alkalinity present, which is just another way of saying buffering capacity...I like the term carbonate alkalinity because the term "buffering capacity" limits the scope to acid buffering only...Making it appear that it is only a function of pH. It is not. 

Eric your blanket use of the terms "best" or (or even"cheapest") are rather subject to set and setting aren't they? I might say that the "best" and "cheapest" buffer is my KOH, since it is a much stronger base, and it is also free. Made from the ashes from wood that I heat my home with, and some rain water. It is "sustainable" it is "free" and it is "strong", so to me, in my set and setting it is "best". Catch my drift