March 6, 2013 Aquaponics No Comments

Some of us are not so science-savvy and don’t have the slightest clue about all this “make sure your water is balanced” and “pH level” talk, so I’m going to try my hardest (I’m not the best at science either) to explain what this all means so that we can answer one of the most important questions for an aquaponics farmer:

Are my fish living in toxic water?!

I’m pretty sure I remember learning about pH levels in 10th grade science, but that was kind of a long time ago so I had to refresh my memory and do a little bit of research. <br/
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So first things first: what is pH?
pH measures the activity of the (solvated) hydrogen ion. Pure water has a pH very close to 7 when it is at 25°C; solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic or alkaline. You want your pH levels in your aquaponics system to be balanced so you don’t harm your fish- many people keep their levels between 6 and 7. Measurements can be done with a glass electrode and a pH meter or using indicators.

How do the levels change?
Fish excrete ammonia in their waste and through their gills which is then converted into nitrite by one bacteria, followed by nitrate by another bacteria. Both of these bacteria will naturally come to flourish in this environment as long as ammonia is present. Once the ammonia and nitrite is converted, the nitrate is consumed by the plants in the system; this completes the process of removing what would be toxic ammonia produced by fish from the water in a way that benefits the plants. The water is recycled; the fish produce plant food and the plants produce clean fish water. Too much nitrate? If you find your nitrate levels are too high, the problem could be that you do not have enough plants in your system, or enough plants that are large enough to consume the nitrate. To lower the levels you can try the following: stop feeding the fish for a little while so the plants can catch up with the nitrate in the system or add more (large enough) plants. Also try adding some red worms to your system; the composting worms will break down accumulated waste quicker.

What levels of ammonia are too high?
Ammonia is very toxic; lethal concentrations at a pH of 6.5 are 0.73ppm (parts per million), while at a pH of 8.5 only 0.17ppm are considered lethal. Most fish can withstand ±40ppm of nitrate. You want to keep fish that are tolerant to high levels of nutrient, for example catfish or tilapia. Test your water regularly for ammonia, nitrite, nitrate and phosphate.

I hope this makes all the scientific talk a little bit less confusing for you, and you realize how important it is to keep an eye on your levels. You want a happy and healthy aquaponics system; you don’t want your fish living in a toxic environment!

Have you made any critical mistakes with your water levels, or do you have any more advice on balancing the levels?

Written by Aquaponics Team