Do NOT Discount pH
The measure of pH in your aquaponics system can NOT be discounted. It is the key most important factor in keeping your system in balance. The picture to the left gives a detailed description of the nitrification process that occurs in nature. In an aquaponics system, it is the cycle that takes the fish waste (ammonia) from the water and converts it into plant food (nitrates). It is an amazing process that occurs naturally, but can be derailed by a pH that is out of balance.
Without getting too scientific-y, the H in pH stands for hydrogen. Hydrogen plays a very important role in that it has the ability to change the shape of other molecules in a solution, such as protein. Changing the shape of a protein molecule can completely change it’s function. Higher numbers of hydrogen -ions are present in low pH readings, adversely lower numbers of hydrogen -ions are present in high pH readings. Most fish and nitrifying bacteria prefer a slightly alkaline pH (between 7-8). Plants on the other hand prefer a slightly acidic pH (between 6-7). Without proper pH, the friendly bacteria in the nitrification process can not survive. As nitrification slows and eventually stops, the bacteria die, the ammonia (fish waste) in your tanks will rise to lethal levels, and all life will cease to exist. To keep your aquaponic system happy and in balance and the train of nitrification running smoothly down its tracks, you will want to strive for a pH of 7.
The Balancing Act
The balancing act is fairly simple. In an established and healthy aquaponic system, nitrification will naturally drive down pH. Healthy systems have optimum oxygen, correct temperatures, and timing is perfected on the cycling of water. Sounds complicated, but it is not difficult to maintain. Oxygenate the water, keep tanks at a moderate temperature where fish and bacteria are comfortable, and adjust either your timer or bell siphon so that it circulates the volume of your water approximately twice per hour. (approx. 45 off, 15 on) A byproduct of nitrification is nitric acid, which is the reason for the natural decline of pH. In systems with a dKH between 4 and 7, pH typically declines slowly and stable. It is recommended to measure pH weekly in an established system. (Unless your dKH is below 4, then test daily until you raise it above 4) Testing weekly assures you are maintaining that neutral pH of 7. If pH has fallen below 7, use equal parts of potassium and calcium carbonate in small amounts to bolster pH, which double as needed supplements to your system. (Always add slowly, and give your system time to adjust before measuring again.) Some recommend hydroxides to control pH, I do not. The short explanation is, carbonates will give your aquaponic system the needed buffer to protect from large swings in pH. The rest of the explanation will come in another post. 🙂
New aquaponic systems maintain pH in the same way, just need a bit more attention in the beginning. It is highly recommended you purchase an API GH and KH Test Kit to understand the carbonate levels in your water source. Levels of dKH above 4 generally have enough buffer and you should not experience any wild pH swings, however, remember as your system matures, it will create more nitric acid and it’s buffering capacity will decrease. Testing of pH in the beginning needs to take place daily. Additions of potassium and calcium carbonate need to be added in small increments and time given before any more is added to ensure readings of pH are accurate. In time, the system will mature and measures can be taken less often.