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Buffering pH and Alkalinity in Aquaponic Systems

We get quite a few questions through the website from members and one that pops up often is “how much of what should I use to buffer the pH in my system?”. Generally most people will use hydrated lime and often only when their pH become problematic or something goes wrong.  Let me share with you Buffering pH and Alkalinity in Aquaponic Systems with a range of nutrient supplements. Buffering pH and Alkalinity in Aquaponic Systems Let’s take a quick look at some of the nutrient supplements that will work for you, be it aquaculture or aquaponics. We have previously spoken about the importance of Alkalinity in any biological system and it is very much related to your bio filters capacity to remove harmful ammonia but it is also very important to prevent your pH from falling too low. With that in mind, I thought it may be easier to explain how much of what you will need to keep your system stable in terms of pH and alkalinity using some of the more common buffering agents used.  These are represented in the table below and relate to the amount of feed you put in your set up each day. This table is based on a 32% protein feed and may not suit every system set up.  The right column is grams (forgot to add that). If you are running aquaponics, you can generally half the quantities. An aquaponic system due to the nitrate uptake should have a zero change in pH and alkalinity, but due to the various designs and climatic conditions this rarely happens, so it is important to keep an eye on the pH and the Alkalinity. If you are using your grow bed to collect solids and or bio filters the pH will drop.  If your plants take up ammonia (no prior bio filtration) it will drop the pH.  this is especially important as the weather heats up.  If you are in the colder months of the year, the feed rates  will be lower as will be the amount of buffer you will need, so the addition of buffering solutions is related to your feed input. Not everyone will use all of these.  In aquaculture systems hydrated lime, dolomite and baking soda are generally used.  In aquaponic systems the sodium based (orange) are to be avoided as it will accumulate sodium in the system and some plant will not respond well to that.  Overdosing with Chloride will also have negative effects. However you can use the Pinkish (magnesium based) Blue (potassium based) and Green (Calcium based) to help correct any nutrient deficiencies as well as manage the pH and alkalinity.  Though Dolomite will also increase your general hardness and add magnesium.  Avoid changing from one to another buffer within a week of each other. It is always a good idea to mix up the buffer in a bucket of fish tank water and dissolve it well before putting in in the system and always avoid pouring the solution onto the fish.  If you have a sump, that is a great place to add it.  to take that a step further, you can set up a 20 litre bucket with a small tap on it and sit it over your sump and have it drip into the system (very slowly) and automatically add the buffer for you. Always add a little bit, wait 24 hours, check the pH and alkalinity again, then add more as needed.  Buffering your system is a great deal more easier if you do this consistently, instead of in big chunks.  Your system may not use all of the amount listed in the table so adjust as needed and always test ALL of your systems water quality (especially the nitrogen and temperature) before adding anything….

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