pH is critical in aquaponics. Fish and plants both need the same range of pH. Here are some notes on Lowering pH in your aquaponics system.
Adjust pH SLOWLY!
The most important thing when adjusting pH is to do it slowly. If you lower pH too much too fast, it could stress your fish or plants and kill them. pH should be lowered over a week or more, not sooner. Murray from http://www.aquaponics.net.au says that testing pH is one of the most important things you can test and stay on top of.
pH will vary according to what is added (rain, fish, plants). Temperature will also cause your pH to vary. If you are testing for pH, you should measure at several points in the day for an average, or measure at the same time and temperature each day so you have consistent readings.
At the beginning, when you have water without a bacteria colony, pH will fluctuate. This is normal.
When adding water from most municpal taps, the chlorine will off gas, which will also cause pH to change.
Best pH Range for Aquaponics
A healthy range of pH for most fish and plants is 6 to 7. Many plants and fish prefer certain ranges of pH. For this reason, some plants like roses and blueberries will not do well in an aquaponics systems. Also, macronutrients and micronutrients are absorbed by plants depending on what the pH is. Too high or too low and the plants will not be able to absorb the nutrients in the water.
How pH Relates to Aquaculture Breeding
pH also determines aquatic life breeding cycles. As pH changes so will the number of fish eggs that are produced, or if they can be produced at all.
Lowering pH in Aquaponics Systems
As you might remember lower pH is more acidic. Here are some safe additives you can use to lower the pH of your aquaponics system.
- pH Down
- Hydrochloric Acid 1 or 2 caps per 250 gallons
- Acetic Acid (Vinegar)
- Sulphuric Acid
- Maidenwell media or Diatomite (5.2-5.8)
- Iron sulfate fertilizer
Do not use citric acid – it is antibacterial and will kill your filter.
Note: if you have limestone as your gravel, you will constantly have low pH. Your sourcewater might also be the culprit if you top off with a non neutral pH. I’ve also read that injecting CO2 directly into the water might lower pH too.
Raising pH in Aquaponics Systems
Higher pH readings are called “base”. Here are some safe additives you can use to raise the pH of your aquaponics system:
- pH Up
- Dolomite Lime – Calcium Magnewsium Carbonate
- Calcium Hydroxide (hydrated/builder’s/slaked/hydrated limes)
- Potassium Carbonate (bicarbonate)
- Potassium Hydroxide (pearl ash/potash)
- Snail Shells
- Sea Shells
- Egg Shells
If you are using shells, boil, bleach or hydrogen peroxide them first to kill all bacteria. Containing chemicals/ingredients in a nylon stocking or other bag will allow you to remove it easily once you are below 7 pH.
pH Explains Cycling
Cycling aquaponics systems simply means that the nitrfying bacteria are present and the system is stable. By monitoring pH, you can tell what is happening or has happened recently in your system. Especially when starting an aquaponics system, record the pH regularly.