Aquaponics Biofilter Essentials

Aquaponics Biofilter and What You Should Know

An Aquaponics biofilter has essentially 3 components. The flow of water, the grow bed media, and the bacteria. Bacteria usually conjure up a negative image in our minds but be assured that these bacteria are very beneficial. Keep in mind that there are more bacterial cells in our bodies then there are human cells. Ratio of bacterial to human cells

aquaponics biofilterThe aquaponics biofilter accommodates an area where the bacteria can gather together. The media in grow beds and raft type beds afford the essential surface areas for the bacteria to colonize. The tank walls and other surfaces in the aquaponics system also provide sufficient areas for the bacteria to gather.

Technically speaking, aquaponics biofilters aren’t really filters because they don’t actually screen out solid fish waste. The bacteria that form a bio-filter target Ammonia that is produced by fish urine (a smaller amount of ammonia breaks off of the fish solid waste as well). Ammonia is toxic to fish, and because fish are more crowded in tanks then in the wild, the level of ammonia is much higher.

How Bacteria Converts Ammonia From Toxicity to Plant Nutrients

The bacteria start a chemical process called nitrification (I won’t bore you with the formula) that converts ammonia to the nitrate that plants thrive on. This takes place with the assistance of two species of bacteria, nitrosomonos and nitrobacter. In a nutshell, one one them changes ammonia to nitrite and the other modifies nitrite into nitrate.

The take away here is that nitrafication is the connection between:

  • The contribution of the fish excrement in the water
  • The Bacterial activity
  • And the health of the vegetables and plants we want to thrive abundantly.

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Additionally, these chemical processes are a common occurrence in nature and a great example of how an Aquaponics system is a re-cycle ecosystem unto itself.

Is Your Aquaponics Biofilter Working and How Can You Tell?

You can assess your aquaponics biofilter performance  by testing. You can’t see them and you can’t count or measure them, so how can you tell if the bacteria are doing their part in helping the health of your aquaponics system? You can purchase Ammonia test kits along with nitrate and nitrite test strips at most pet stores or online.

Once you have the test kits, use them to find out the levels in the tank water. When the fish are first introduced to your system the Ammonia levels should rise for the 1st dozen days or so. Following that, the nitrite levels should start showing up and Ammonia levels begin decreasing. Then after another ten days you should see nitrate levels increasing and the nitrite levels falling. All and all the nitrafication cycle will naturally stabilize after about 25 to 30 days.

What You Should Know About pH Levels

What is a pH (Parts Hydrogen) level? In an Aquaponics system, the pH level is a measurement that tells us how much acidity is in the water compared to  alkaline (basic). It is measured on a scale of 0.1 -14.0 with anything below 7.0 being acidic, and above 7.0 being alkaline. pH 7.0 is considered neutral, or balanced.

Most plants do best in a pH environment between 5.5 and 6.5 which is slightly acidic. Levels above that would make some of the nutrient elements inaccessible. To be more precise, aquaponic and hydroponic grown vegetables  prefer pH between 5.8 and 6.3.  By comparison, an average tap water is going to be between pH 7 and 8. This is why monitoring your pH levels is so important to the health of your plants. It can determine whether or not your Veggies will have optimal nutrients available.

How does this apply to our Aquaponics fish tank environment? As we mentioned before, nitrafication is the all important factor for the end game-growing superior vegetables. To grow thriving plants the fish need a healthy environment as well. The optimum pH level for the success of the nitrafication process is 7.0 or a little above.  It just so happens that this is also the best pH level for the health of the fish in your Aquaponics tank. Remember that nitrafication is the process of converting ammonia to nitrates (nutrients for plants).  Ammonia build up in the tank is toxic to the fish, so it’s important to monitor this pH media as well.

The pH can vary due to other factors like the buffering capacity. This is the capacity of the water to resist changes in pH also known as hard water. Other factors can be the temperature and chemistry of the water in your system. This is why you need to monitor your pH level from time to time to keep your aquaponcs system running precision sharp.

pH MeterWhat can you do to alter the pH level to neutrality? First you’ll need a pH test kit. Kits come with test strips and some even have meters to test the pH levels.

To raise the pH level some aquaponics gardeners use calcium hydroxide with potassium hydroxide. These not only raise the level to 7.0, but are a supplement to plants that are deficient in potassium and calcium. There are other alkaline chemicals that work but be sure they are not toxic to the fish.

For lowering the pH when the water is too alkaline, phosphoric acid is recommended. Carbonate buildup is usually the culprit when the water becomes too alkaline. Some gardeners try organic ways of lowering the pH by adding distilled or rain water to the tank.

If these don’t work another option is to spend some money on a fish tank bio filter. They come in a variety of shapes and sizes depending on how many gallons of water are in your tank.

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