Aquaponics Frequently Asked Questions
The answers given here are for general information only and can not, by their nature, take into account every circumstance. Please review the answers in light of your actual circumstances and if you are unsure seek further advice before doing anything. If you use this information you do so at your own risk.
Questions
General
- What should I test for in my system?
- What do I do if the water in my system starts to smell?
- What is the best fish for a home system?
- What plants can I put in the an aquaponics system?
- How much should I feed my fish?
- How often should I feed my fish?
- If the new leaves on my green plants are yellow what can I do?
Nitrification
- What is Nitrification?
- Is Nitrification important?
- Do I have to buy Bacteria to add to my system?
- How do I know if Nitrification is happening in my new system?
pH
- What is pH?
- What is a normal pH for an aquaponics system?
- What is the correct pH range?
- My pH is too high what do I do (pH greater than 7.5)?
- My pH is too low what do I do (pH less than 7)?
Pests and Diseases
- Why can't I use chemical pesticides?
- Why can't I use anti-bacterial treatments on the fish?
- How can I control Caterpillar's?
- How can I control Powdery Mildew on my Tomatoes?
Kits and Systems
Answers
What should I test for in my home system?
We recommend that you test for pH, Ammonia, Nitrite and Nitrate. You can get a fresh water test kit from most Aquarium shops that will do these tests.
What do I do if the water in my system starts to smell and becomes 'cloudy'?
Firstly test the water. If you can not do that or you get a very high reading of Ammonia or Nitrite then we suggest you release about one-third of your water and top up your system up again.
If you have tested it and the Ammonia and Nitrite are not too high then stop feeding the fish for a couple of days. They will survive without feeding for a few days and the water should clear.
After either of the above review how much you are feeding your fish as you are probably overfeeding them. Remember that when the water temperature drops the fish will eat less.
What is the best fish for a home system?
There is no 'best' fish. It depends on what is available to you, what is legal for you to keep in your location and what will live in your temperature range.
The qualities we recommend for a fish for a home system when a person is starting are:
- reasonably tolerant of Ammonia;
- able to survive at least 5 Degrees Celsius either side of your maximum and minimum ambient air temperature;
- will easily take to pellet (fish food);
- is happy in a tank; and
- will not eat each other including fingerlings.
In South East Queensland we find Silver Perch fits the bill very well.
What plants can I put in the an aquaponics system?
There have been over 300 different plants that have been tested that will be happy in an aquaponic system. The major group that will not grow in an aquaponic system are root vegetables.
Basically the list is too long to write and is dependent on your location. If it is an above ground plant that grows well in your area and does not mind getting it roots wet then you should give it a go.
How much should I feed my fish?
The amount will vary depending on the type of fish, the temperature of the water and the type of food you have. The general rule in warm weather with commercial fish food is about 3% of their body weight when they are small fingerlings and about 1% of their body weight once they are no longer fingerlings.
Most people grossly overfeed their fish so please weigh your feed when you first start. This will give you a good idea of how much you are feeding the fish.
How often should I feed my fish?
In a home system we feel that you should feed your fish morning and night. As close to 12 hours apart as possible.
If the new leaves on my green plants are yellow what can I do?
If your plants are starting to go yellow it is most likely because your system is low in Iron. Add some Chelated Iron to your system. A teaspoon of Chelated Iron mixed in a bucket of water and added slowly into your grow beds should do the trick.
You might notice your system goes black or very dark in colour after you do this. That is fine, don't worry about it and it will clear in a few days.
What is Nitrification?
The process whereby Ammonia in wastewater is oxidized to Nitrite and then to Nitrate by bacterial or chemical reactions. Basically there are Ammonia-oxidizing bacteria (AOB) that convert Ammonia into Nitrite in the presence of oxygen for energy. Nitrosomonas is an AOB. Then Nitrite-oxidizing bacteria (NOB) convert Nitrite to Nitrate in the presence of oxygen for engergy. The most common mentioned NOB is Nitrobacter however some modern studies suggest that Nitrospira is perhaps a more important NOB.
Is Nitrification important?
Yes, it is very important because Ammonia and Nitrite are very toxic to fish. Nitrate is not as toxic to fish and the plants can use it to produce protien and nucleic acids.
Do I have to buy Bacteria to add to my system?
Generally no. So long as you do not overstock with fish and keep monitoring your system for pH, Ammonia, Nitrite and Nitrate.
How do I know if Nitrification is happening in my new system?
You should get a test kit that does pH, Ammonia, Nitrite and Nitrate. What you should see, after you put the fish into the system, is an increase in Ammonia.
The Ammonia should keep increasing. Over this time Ammonia-oxidizing-bacteria (AOB) will commence to multiply. They are typically slow to multiply. Once there are enough AOB the Ammonia should decrease. This should start within one and half to two weeks.
Nitrite should now start to increase in the system as AOB convert the Ammonia. As the Nitrite levels increase the Nitrite-oxidizing-bacteria (NOB) will begin to multiply in the system and the Nitrate level will start to increase. NOB are equally slow growing bacteria and it will typically take a week and half to two weeks before the Nitrite level will peak and then start to decrease.
By now, if everything is going well, the Ammonia should be very low and remain like that. Nitrite levels should continue to drop over the next few weeks until it remains at a low level. Nitrate levels will vary depending on the balance of fish and plants in the system.
pH should decrease over the period as the nitrification process will make the water more acidic. Keep a track of this. pH must be above 7 for the nitrification process to work properly.
What is pH?
pH is a measure of the degree of the acidity or the alkalinity of a solution as measured on a scale (the 'pH scale') of 0 to 14. Technically it is a measure of the activity of the hydrogen ion (H+).
The midpoint of 7.0 on the pH scale represents neutrality. pH 7.0 is called a 'neutral' solution and is neither acid or alkaline. Numbers below 7.0 are known as acid. Numbers greater than 7.0 are known as alkaline.
What is a normal pH for an aquaponics system?
There is no 'normal' pH in an Aquaponic system as such. The pH level will change over time depending on the system and how it is running.
The system will not settle on a particular pH and stay there. This is why it is a good idea to test the pH at least once a week.
What is the correct pH range?
The pH in an aquaponic system should be maintained between 7.0 and 7.5.
My pH is too high what do I do (pH greater than 7.5)?
This is usually ok and you do not have to do anything to 'fix' it. The nitrification process will cause the system to become more acidic over time. We have had systems with pH levels just over 8 when they started and they all went down over time.
My pH is too low what do I do (pH less than 7)?
It is normal for the system to get more acidic. The problem is that below 7.0 the nitrification process will slow dramatically and stop by the low 6's. It is important that you do not let this happen!
You can increase the pH of the system (make it more Alkaline) by adding Calcium Hydroxide [ Ca(OH)2 ] "Hydrated Lime" or Potassium Hydroxide [ KOH ] "Caustic Potash". In both cases be very careful.
Add a small amount of the powder to a bucket of water. Then pour it into your system slowly over a prolonged period (like a day). Remember it is very Alkaline so do not just dump it all quickly into the system.
Note: Calcium Hydroxide is reasonably safe however Potassium Hydroxide is not. Both however should be handled with care.
Why can't I use chemical pesticides?
Most chemical pesticides will kill the fish.
Why can't I use anti-bacterial treatments on the fish?
Anti-bacterial treatments will also kill the Ammonia-oxidizing-bacteria and the Nitrite-oxidizing-bacteria. Obviously this is not good as it will stop the nitrication process.
How can I control Caterpillar's?
A bacterial Bacillus thuringiensis (Bt) is used to control caterpillars in some commercial and experiemental systems. Yates 'DIPEL' product contains the bacterial.
Garlic spray can be used as a repellent and to kill caterpillars if you do not want to use Bt. Also there are many other 'organic' methods that you can try.
How can I control Powdery Mildew on my Tomatoes?
We find that removing the effected leafs and spraying milk on the remaining leaves works very well for us. The milk spray is 1 part fresh milk and 4 parts water. It will help control the fungus and will not kill fungus eating Lady Birds. You may need to spray weekly.
What is the advantage of a Kit?
You do not have to figure out and look for all the parts. This can take hours or more likely weeks. So you can be up and running much more quickly.
You will get a system that has been tested and will work if managed correctly. You will get support in building and running your system.
Do you do customized systems?
Yes. If you would like us to design a system specifically for your needs then please contact us.
For more Information please do not hesitate to contact us.
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| Kerri Kempin | Martin O'Dee |
Last Modified: Saturday, 09-Feb-2008 18:50:29 EST
