pH always running high

[Cameron Smith]

I have a 10-gallon fish tank and a 1:1 tank to grow bed ratio. I also have a sump that holds between 5-7 gallons at any given time. This is my starter system, and I have had a lot of fun and learning with it so far. I plugged in the pump on November 26, and today I tested the water and the results show that I have a FULLY CYCLED AQUAPONICS SYSTEM!

That said, I am having a pH problem. My pH levels are constantly high. They hover around 8.2-8.4. The first time I tried adjusting it, I used vinegar. I added a tablespoon at a time and waited 20 minutes for it to mix into the system, then tested. I brought the pH down from the aforementioned range to 7.4. The next day it was right back up to 8.4. I figured the weak acid had worn off, so I bought the pH decreaser (shown below) from the pet store and added about .75 ml to the system and waited. The next test showed a pH of 8.0. I thought, "good, it's working, just need more." So I added another 1.0 ml of the acid and waited. The next test went to 6.2!!!! So I figured maybe I should have waited longer before adding more and retesting. I decided from then on I would only make one intervention per day to give the system more time to stabilize between tests. Anyway, the next day the pH was back up to 8.4. I have not intervened in the system for 7 days. My bacterial cycle has been progressing, my seedlings are growing, and my fish are hardy and eating well. I know it's not ideal, but I figured I'd accept it for now and try to lower the pH once the nitrogen cycle had leveled off. 

So a few questions are in order: 

1) How bad is it really that my pH swung so violently in these couple days? How bad is it really that my pH was at 8.4 to begin with? 

2) Now that my water is cycled, should I expect my interventions to lower the pH to stick more than a few hours? Sylvia's book says during cycling pH rises and during normal operations sometimes you have to try to keep it from falling. 

3) I know that the smaller the system, the more rapidly changes can take place. Mine is about as small as you can get! When people say this about the tendency of smaller systems to be less stable, what are the kinds of conditions that cause it? Now that my water is cycled, unless I add something to the system that shouldn't be in there, what will cause changes in my system, other than the normal "wear and tear" mentioned in question 2 above? 

[Rob Torcellini]

what's your growing media?

[TCLynx]

Yep, what is your growing media?

And

What about your tap water?

Here is a blog post about tap water, measuring the pH right out of the faucet is likely giving you a false reading.

PH and Tap water

Starting up a system with a pH of 8.2 is not that terrible though your plants may struggle a bit and adding some chelated iron regularly will help them much.

Bouncing the pH though is really hard on your bacteria, plants and fish if you have them.

I recommend doing your pH adjusting on your top up water before you use it in the system.  Hopefully you have an extra air pump and air stone you can use to help mix the water and aerate it in your water prep bucket.  I would adjust your top up water pH down to between 6-6.5 (hopefully get it to a level that you can tell what the pH is since if you read 6 it could be 6 or anywhere below 6 and you don't actually know.)  Anyway, add acid and then let the water bubble and mix and check it again several hours later, then check it again the next day.  Add more acid if necessary and repeat the wait/test/wait bit until the pH stabilizes.  Hopefully you measured how much water and how much acid it required to become stable at the desired pH.

Why this bouncing of pH?  Well, if your water has carbonates/bicarbonates in it the acid will dissolve them which buffers the pH back up until all the carbonates/bicarbonates are use up so to speak.  If you initially add too much acid you might use up all the buffering and wind up with a way low pH.  If you don't add enough the pH may drop initially and then the buffers dissolve and bring the pH back up.  Even if you add just the right amount, the pH will drop low until the buffers dissolve at which point hopefully the pH will come up to the exact level you want.  But as you can see, even if you add the right amount the pH is still going to bounce which is hard on living things, hence why you should do any acid work in a separate container from your system.  Keep in mind any acid will likely leave something in the water so you want to make sure it won't be building up to dangerous levels for your plants.  I've used hydrochloric acid (muratic acid) the reaction there is that the acid reacts with the carbonates/bicarbonates (mostly calcium carbonate or bicarbonate in my water) the resulting CO2 is bubbled out of the water and the left over in the water is the salt calcium chloride.

Now I don't know what the primary ingredient of your pH product is there but it may be Sodium BiPhosphate.  I'm not sure what the chemical reaction is going to be there but I don't like to add extra sodium to a system except when I need to salt for new fish or to treat a disease to protect the fish from a nitrite spike (and for that you use sodium chloride or salt since it is actually the chloride ion that protects from the nitrite.)  Plants use sodium but very very little of it so I wouldn't want to be adding sodium regularly because it would build up.

Remember that most chemicals used for aquariums, they figure you will be changing out the water not just topping up and since we don't normally change out our water in aquaponics, we must be very cautious of using any aquarium chemicals or medications since they would build up and they are also usually not tested for using in a food system (heck many of them don't even disclose what the ingredients are.)

[Robert Rowe]

Cameron

I had similar issues when I first started but finally decided to stand back and see what nature would do as the plants in my media and raft bed progressed. I started back in July and now my PH is running @6.8-7.4 and I am not chasing the numbers.

 

[Cameron Smith]

HAH! I actually was just blowing through a PVC pipe to mix in the pH decreaser I was planning to add to the system tomorrow. I didn't even think of the necessity of aerating the water, but I'm sure this works just fine as well without the need for extra equipment. I didn't know that about the tap water carbonates. I'm going to have to work several days ahead of time to store off-gassed, pH adjusted water to add to my system. 

I live in Las Vegas where the water comes out of the tap with a pH of 8.2. At least for now--Sylvia wrote how the water sources may change seasonally. But yes, my water has a high pH. I just spent about 30 minutes trying to adjust 5 gallons of tap water down to a pH of 7.0-7.2 because right now my system is at 7.4. I'm starting to see that the wait/test/wait routine may have a lot more virtue than I had even understood in my previous posts. The problem is my system and my management routine are so new I haven't really worked in having a pre-adjusted water source to add to the system when it is needed, and again...with it being so small, water dissipates quickly and I find myself suddenly listening to a whining pump that is no longer submerged with water. So even now as I'm trying to look ahead to have water ready for tomorrow, it still may not be enough time to get the water stabilized and ready to go into the system. I'm guessing that with all the adding tap water that is off-gassing along with trying to alter the pH of the current system water, I'm really pissing in the wind here. (BTW, don't know if it matters, but I tested my tap water with the beta strips and it shows safe levels for chlorine, so I have been adding it straight from the tap with minimal adjusting for pH and temp as needed). 

I am using the pH decreaser shown in the picture in the OP. It is TopFin brand "pH decreaser" which says on the bottle it contains sulfuric acid. Come to think of it, sulfur is a salt...wonder if that's bad for my system. I couldn't find pH Down, the product specifically mentioned in Sylvia's book, at the stores I went to. 

Thanks very much for the input, folks. 

TCLynx said:

Yep, what is your growing media?

And

What about your tap water?

Here is a blog post about tap water, measuring the pH right out of the faucet is likely giving you a false reading.

PH and Tap water

Starting up a system with a pH of 8.2 is not that terrible though your plants may struggle a bit and adding some chelated iron regularly will help them much.

Bouncing the pH though is really hard on your bacteria, plants and fish if you have them.

I recommend doing your pH adjusting on your top up water before you use it in the system.  Hopefully you have an extra air pump and air stone you can use to help mix the water and aerate it in your water prep bucket.  I would adjust your top up water pH down to between 6-6.5 (hopefully get it to a level that you can tell what the pH is since if you read 6 it could be 6 or anywhere below 6 and you don't actually know.)  Anyway, add acid and then let the water bubble and mix and check it again several hours later, then check it again the next day.  Add more acid if necessary and repeat the wait/test/wait bit until the pH stabilizes.  Hopefully you measured how much water and how much acid it required to become stable at the desired pH.

Why this bouncing of pH?  Well, if your water has carbonates/bicarbonates in it the acid will dissolve them which buffers the pH back up until all the carbonates/bicarbonates are use up so to speak.  If you initially add too much acid you might use up all the buffering and wind up with a way low pH.  If you don't add enough the pH may drop initially and then the buffers dissolve and bring the pH back up.  Even if you add just the right amount, the pH will drop low until the buffers dissolve at which point hopefully the pH will come up to the exact level you want.  But as you can see, even if you add the right amount the pH is still going to bounce which is hard on living things, hence why you should do any acid work in a separate container from your system.  Keep in mind any acid will likely leave something in the water so you want to make sure it won't be building up to dangerous levels for your plants.  I've used hydrochloric acid (muratic acid) the reaction there is that the acid reacts with the carbonates/bicarbonates (mostly calcium carbonate or bicarbonate in my water) the resulting CO2 is bubbled out of the water and the left over in the water is the salt calcium chloride.

Now I don't know what the primary ingredient of your pH product is there but it may be Sodium BiPhosphate.  I'm not sure what the chemical reaction is going to be there but I don't like to add extra sodium to a system except when I need to salt for new fish or to treat a disease to protect the fish from a nitrite spike (and for that you use sodium chloride or salt since it is actually the chloride ion that protects from the nitrite.)  Plants use sodium but very very little of it so I wouldn't want to be adding sodium regularly because it would build up.

Remember that most chemicals used for aquariums, they figure you will be changing out the water not just topping up and since we don't normally change out our water in aquaponics, we must be very cautious of using any aquarium chemicals or medications since they would build up and they are also usually not tested for using in a food system (heck many of them don't even disclose what the ingredients are.)

[Cameron Smith]

My growing medium is aquarium gravel. 

Rob Torcellini said:

what's your growing media?

[Cameron Smith]

Yeah, I'm starting to learn this in many areas of my life at once, how to focus on the long term and work with less jilting stops and starts. I like your use of the phrase "chasing the numbers". I really am. I just need to wait and see. Everything is progressing. It's not perfect, but it's working and I can always make improvements, but I don't want stress anyone out. I have millions of lives at stake here. 

Robert Rowe said:

Cameron

I had similar issues when I first started but finally decided to stand back and see what nature would do as the plants in my media and raft bed progressed. I started back in July and now my PH is running @6.8-7.4 and I am not chasing the numbers.

 

[Jon Parr]

Cameron, it sounds like you've got good advice here, and things will mend. You came to the right conclusion in the OP, to adjust and measure only once per day. It takes time for the carbonates in the system to "wake up" and neutralize each day's additional acid. Eventually, though, all the carbonates will be dissolved, and matched to an equal number of acid components (7.0), and you'll gt stability (7.0 the next day). When that happens, the additional acid will lower the pH more permanently, and the following day will read less than 7. At this time, the acidifying process of nitrification will continue to lower pH, and you will see a daily drop, without additional acid. For many, simply adding carbonate-rich top up water is enough to counteract nitrification, and keep the pH in your desired range. Don't get too complacent, though, check pH at least every few days.

The pH bouncing is hard on the system, but don't worry about the past. Acids and pH down, especially sulfuric, are fast acting, and fast changes are what we want to avoid. So like TC said, adjust your top up water first, retest a day later, then use the doctored water to lower your system pH. Much more gentle. Adding rainwater or RO water will also lower pH very gently, not so much because they are themselves acidic, but because they contain no buffers, thereby allowing your nitrification to eat up carbonates faster than they are being added. If you have carbonate tap water, pH can often be controlled just by adding tap water or rainwater, depending on the change you wish to make.

I'd be careful, BTW, about assuming the chlorine or chloramine in city water is safe to add directly to your system. It shouldn't be safe if coming from the tap. If it is, it might not be tomorrow, when the city realizes the mistake. I know a lot of people who add tap water directly to systems, trusting that the bacterial load (and hardiness of the fish) can take the burden. To me, better safe than sorry.