Starting with good water is the only way to go. Whether it is rainwater, RO(reverse osmosis) water, or well water, you just need to know what is in your water to start with.
Do not use chlorinated water because it will kill the bacteria and fish that support your system. Frequently city water is chlorinated, but is not unheard of to have well water with trace amounts of chlorine. When in doubt have your water tested.
If this is the only source of water you have, place the chlorinated water with a small air pump running 24-48 hours and the chlorine will evaporate out of the water making it safe for your fish. This just takes a little time but is easily corrected.
Water Quality Terms you need to be familiar with to maintain a balanced system.
PH - alkaline, acid, or neutral (PH of 7)
EC (electrical conductivity) - the degree to which specified material conducts electricity, calculated as the ratio of the current density in the material
TDS (total dissolved solids) - In aquaponics, total dissolved solids can indicate the quality of the water and the nutrient concentration
GH (general hardness) - Water hardness is a measure of the amount of calcium and magnesium in the water and is expressed in ppm (parts per million) of calcium carbonate
KH (alkalinity) - Carbonate hardness (KH), is also known as alkalinity, is the measure of a water's buffering capacity in an aquaponics system
Iron, Phosphorus, Potassium , Calcium, Magnesium - vital nutrients for the growth of plants
Ammonia, Nitrites, Nitrates - The cycle of fish waste to plant output
Temperature - The temperature of the water for optimal fish health
DO (dissolved oxygen) - the amount of oxygen gas that is present and dissolved in the water
All of these can be monitored to control water quality but only a few have to be monitored constantly such as PH, ammonia, nitrites, and temperatures to assure the health of the fish and plants(refer to the sections monitors and test equipment for more information on each of these and how they are tested and maintained)
PH In the simplest terms, is how acidic or alkaline the water in your aquaponic system is. It is measured on a scale of 1-14, 1 being the most acidic and 14 being the most alkaline. pH is important to your plants’ ability to uptake the nutrients essential to health and productivity. Having an aquaponic system with a pH that is too high or too low will block your plants’ ability to absorb the nutrients necessary for growth, which leads to plant growth problems and will also affect the bacteria and fish inside the aquaponic system. Ph must be maintained as a mature aquaponic system will constantly be lowering the PH. As there is no absolute perfect PH level, a range of PH 5.9 to 6.6 is optimal for plants to uptake certain necessary minerals. Bacteria love a PH of 7 to 8, and stop working when the PH falls below 4 or goes above 11. The fish all have different PH levels in which they thrive, but most fish enjoy a neutral PH of 7. Do your research before choosing your fish.
As you see there is a wide range of PH these bacteria, fish, and plants need to thrive, and you must decide what you are wanting to do. Most aquaponic systems are driven towards the plant production and run a lower PH. If your main concern is with the fish, you will be limited on your plant selection as a higher PH limits the uptake of certain minerals to many plants such as Iron and can slow the growth of some plants. There are ways around everything such as using a high PH chelated iron, but some of these iron products can stain the water red. This red water doesn't hurt anything other than the view of the fish. Cover as much of the water surfaces as you can from the light. Your fish tanks, sump tanks and any other place that light can get to the water needs to be covered. Algae will grow rapidly in the water especially with the high mineral content in the water if exposed to light. Algae can cause PH swings and other water quality issues if left untreated.
There are 16 nutrients that play a role in overall plant health and are essential for optimal yields. I recommend keeping the pH of your reservoir water between 5.5 and 6.5, or even better, between 5.8 and 6.3.
Here’s a chart to explain why:
A balance of the above minerals and nutrients is needed for plant health.
Stay tuned for next month's blog on choosing fish and plants for your aquaponic system.
Joe Leveridge
TXUS Farms
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