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Lowering pH of Tapwater ChemicallyQuick Links: |
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So...if you're lazy like I am, and the water out of your tap has relatively low carbonate buffering (kH less than 4) with medium hardness or less (GH less than 10 or TDS 170uS or less) then CONGRATULATIONS!!! You may qualify to use your tap water for mixing up low pH water for your Macs. The biggest difficulty that people have is not lowering the pH, but keeping the pH at a stable level. I'm sure that many of us have heard the advice "it should be alright as long as the pH is kept constant". I for one agree with that, provided that the pH is within a reasonable range for the particular type of fish in question. It is better to have a constant pH on the high end of the acceptable range rather than have a lower pH and have it bouncing around. Constant pH changes will severely stress any fish. If you want to know more about pH buffering capacity and why for most of us "pH DOWN" doesn't work, then read on.... Otherwise if you want to skip to the actual mixing, click HERE. pH BUFFER THEORY WARNING! SCIENCE CONTENT! This section might be boring like hell to most of us out there, but i can say from experience that once you get it, it's like your eyes have finally been opened and mixing low pH water is no longer a mystical science. I promise that i'll try to keep it as unscientific as possible. Since we are trying to achieve a low pH (perhaps for macs), i'll make all explanations with reference to acid buffers. Firstly, what is a buffer??? Scientifically, it is an aqueous solution of a weak acid in the presence of its conjugate base or a weak base in the presence of its conjugate acid. This definition is good and all, but what it really means is this: A buffered solution is one that can "absorb" a certain amount of acid or alkali without large changes in its own pH. So now we know why when we try to add "pH down" to tap water the pH rebounds. The tap water is actually being buffered by carbonate buffers (which has to do with kH). It is this carbonate buffer that allows the added acid ("pH down") to be absorbed without a large change in its own pH. Hence... although most people don't realize it, TAPWATER IS ACTUALLY BUFFERED. Only 100% pure water such as distilled water has little or no buffering capacity. This is quite evident when you try to add "pH down" to 100% distilled water. The pH just drops and stays down without rebounding. Now that we know what a buffer is, we need to realize that each buffer solution has a buffering capacity or a limit. It is impossible to expect the tap water pH to rebound forever if we keep on adding "pH down" forever. Eventually, the buffer will give out suddenly and is no longer able to keep holding the pH up. We get what is commonly known in the aquarium world as a "pH Crash". This is when the pH suddenly falls to "super acidic" and is not able to pick itself up. Thereby killing everything in the tank. It is important to note that different chemicals buffer water at its own unique pH. Some may buffer at a more acidic pH, and vice versa. As it turns out, carbonate buffers (in most tap water concentrations and proportions) tend to buffer at a pH which is higher than 7. Other buffers such as Phosphate based buffers (Such as "pH down" or "Acid Regulator") tend to buffer at more acidic pH's. Hence, in order to mix up a acidic buffered water for macs, we can either 1) Start with very poorly buffered water such as R/O water or distilled water (which we know tends to be wasteful or expensive) or 2) Somehow chemically remove the buffering capacity of tap water and then replacing that buffering capacity with our own buffer which is able to buffer at low pH's. (Much cheaper and easier if your tapwater is suitable) WHAT KIND OF BUFFER TO USE? There is a plethora (yay! I actually used one of my SAT words in a sentence!!) of products out there which is sold for aquaria use. Note that they often come in antagonistic pairs such as "acid buffer and alkaline buffer" or "pH up and pH down". This is actually significant and we'll discuss this later. We are all familiar with "pH down", "acid regulator", "neutral regulator" etc. So which one to choose?? The ultimate decision should be based on 3 factors. 1) What is the pH of your tapwater now and where do you want it to end up? Obviously if it is really low and you want to keep african cichlids, you want to get some sort of Alkaline buffer. The opposite is true if you want to keep wild discus or Macs. 2) What is the current buffering capacity of your water? Most of the time, this usually means what is your kH. A high kH means that your water is "highly" buffered by carbonates and a low kH means that it is "lightly" buffered by carbonates. Water with a low kH is easily adjusted to become more acidic but is sensitive to pH crashes. If you have a high kH and you just want to lower your pH by a little, any products which claim to "lower kH" will do. But if you need to lower you pH by a lot (like so much that the kH becomes zero) then just simply adding acid will not do. This is because without any buffering, you are very prone to a pH crash. 3) Is your tank planted?? Ok.. the first two were easy to understand, but what does a planted tank have to do with buffer choice? Easy... Most commercial pH adjusters and buffers out there are phosphate based. Many of us know what phosphate is..... FERTILIZER FOR ALGAE! To prove my point, as i was updating this page, one of my readers sent me an e-mail saying "The plants get new light syndrome or something, I mean the algae that make green water is blooming." (used with permission original spelling retained.) Hence, my take on this... if you are going for a planted motif (which is highly recommended for Macs), then i would stay away from anything that says "Phosphate Buffer" on the label. If you are content with a Bare Bottomed tank and partial water changes every few days, then i say go for it! Because phosphate buffers are one of the strongest buffering agents that we have for aquaria. They keep the pH very stable which is good for the fish.
So what about Macs?? I keep my Macs in an average of pH 5.5 (way too low for carbonate buffering) and in planted tanks (so Phosphate buffers are a no-no). So far, the only product that i have found that I have great success with is "Acid Buffer and Alkaline Buffer" from SeaChem. Both are non-phospate (and apparently non carbonate... dunno they are keeping it hush hush??).
Here are their product pages: http://www.seachem.com/Products/product_pages/AcidBuffer.html http://www.seachem.com/Products/product_pages/AlkalineBuffer.html I have found their name to be slightly misleading (not to mention confusing) as they are not true buffers on their own(see scientific definition at the top of page). However when mixed with each other or with other buffering systems (like carbonate buffering that is already in water), they form an acid / base conjugate pair which is a moderately good buffer. This is where the earlier mention of the antagonistic pairs come in. Remember the goal is to somehow "remove" the buffering capacity of the carbonates that are already in the water and then replace it with something else. This is what we will attempt to do with Acid Buffer and Alkaline Buffer. In short: 1) Add "Acid Buffer" to water until kH becomes zero (i.e. pH crash because there is no more carbonate buffering capacity) 2) Add "Alkaline Buffer" back to water to form a new buffered solution using the conjugate base inside "Alkaline Buffer". (remember that a buffer is a weak acid with its conjugate base) Confused?... yes... so was I... and the name acid/alkaline "BUFFER" is not helping because it is not a real buffer. Just read it through a couple of times. Otherwise, you'll just have to take my word for it for now... until i find a better way to explain it.
MIXING PROCESS Ok... finally, lets get to the nuts and bolts of mixing water using Acid and Alkaline Buffer. I'm not going to discuss theory here, but simply give you cookbook steps on mixing. If you have read through every single line above and understood it, then what we are about to do will make perfect sense to you. Note that the method here is not only for macs, but for adjusting water for any conditions. The goal of this recipe is to determine the proportion of water to chemicals ratio to use. If you have accurately followed the steps below, by the end of this exercise you will be able to determine "recipe" which is unique to your water. For Example, 5 gal tap water with 2 Tbs Acid Buffer and 1 Tsp of alkaline buffer will give me about pH 5.8. The below steps are for "first time mixers" who are trying to find out how much of alkaline and acid buffer to use. Remember to record down how much of each chemical you use. I know the following steps make mixing seem like a daunting task, but if you have recorded down the correct amount of chemicals used, then for future batches, you just have to mix the same proportion and not have to go through all this again. Equipment / Ingredients Bottle of "Acid Buffer" Bottle of "Alkaline Buffer" Mixing Container. e.g. 5 gal bucket or 50 gal drum pH tester. Digital pH meter is HIGHLY recommended!! (you'll see why soon enough...) Something to "Mix" the water. For small quantities, an airstone will be sufficient. For larger volumes, a submersible pump will do fine.
Step 1: Determine if your water is OK for mixing. Record the amount and type of water used (eg. 5 gal of 50% RO/Tap mix) Step 2: Add Initial Amount of Acid Buffer Example: Target pH 5.8, Starting pH 7.8. Step 3: Allow Time For pH Rebound Example: (Continuation of step 2 above) Step 4: Repeat Step 2 and Step 3 Until pH Crash You will note that each subsequent rebound will stabilize at a pH that is less than before. The rebounded pH will continue to fall until it "Crashes" where it will fall drastically and not return again. Example: Continued from step 3 above. pH is now 6.8 Step 5: SLOWLY add Alkaline Add alkaline till it's just shy of the target. For example, say the target is 5.8, you want to stop adding when the pH is 5.6 or so. This is to guard against any overshoot. Remember to record the amount of alkaline used. Example: Continued form step 4. pH has just crashed and has been sitting at 3.1 for 5 hours. Step 6: Fine Tune Example: pH is now 5.6, target is 5.8. 5 gal bucket of water. Step 7: Allow water to sit If you have faithfully recorded everything, you will end up with a recipe as follows: So the next time you mix, you simply have to measure the above amounts (less the fine tune) and just mix it right away in the bucket. You will end up with a pH close to your target pH. So all you need to do is fine tune. If you actually bothered to read everything up till this point, then congrats! You earned yourself a reward for being so diligent! A fellow aquarist did everyone a great service and took it upon himself to create a flowchart of the above mentioned steps. If you are the visual type, then it might be worth checking this out: Other Things To Note: Sometimes the chemistry of our water supply might change according to the seasons or for other reasons. So make sure you make adjustments accordingly. But for the most part, your "recipe" should work for most of time. If using 100% R/O water, the "recipe" that is found on the bottle is quite accurate. All you need to do is "fine tune". BE PATIENT! It doesn't help anybody to rush through and mess it up. Even though it may take 2 or more days to do it the first time, but once you get your own unique recipe going, it shouldn't take more than a 6 hours for each subsequent mixing and fine tuning. PLUG On the urging of my friends, I started this website by putting together the original (and quite successful) B. Macrostoma pages. Since then it has grown to include much more aquarium related information. All this time I've provided all this info and lots of free e-mail support to anyone who needed help. The advertising on this page helps out a little to offset the cost of webhosting. So if you see something that you may be interested in listed within the GoogleAds banners, then please don't hesitate to check it out. I thank you all for your great interest in my articles and I hope to keep hearing from you guys, even if it is just dropping me a note to say hi. God Bless! |
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