Aquaponic Gardening

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I have noticed a number of discussions lately, and have experienced my own experiments going in the same directions sometimes - a bit too much haste.  Mixing water is not like mixing paint.  Imagine you went to the paint dealer, asked to have a colour mixed up and then get told to wait two days to three weeks, depending on the type of paint, to see where the colour ends up.

 

Well that is a bit how water chemistry in closed recirculating systems should be approached.  Just adjusted your pH? The reading you are getting is not accurate yet.  Just fed your fish or had some cold days recently? Test over a couple of days to be sure about your DO.  I see the most common issues people address is pH and cycling of a new system.

 

In terms of pH, few people seem to test a range over a number of days to see what is going on in their system.  Depending on your water temperature, fish activity and alkalinity, it may take a number of days for the addition of new water or the adjusting of pH to fully manifest in the pH readings.  A case in point is an experiment I'm setting up to make sure that I know what an experimental mix of media is doing to my water chemistry.  I tested my rain water supply and it was 6.5.  I decided that this was too low and adjusted upwards until the immediate reading was 6.9.  This was left to stand for two days, after which the pH was 6.7.  Now if the experiment had started, I may have chalked up the initial shift to the media.

 

TC Lynx often warns people about testing well or tap water out of the tap immediately for similar reasons.  Any chlorides or CO2 in the water could affect your reading, thus let it stand for a bit or if you have to add to your water immediately, test the effects over a number of days.  I also suggest keeping track of a number of water quality variables and learning to understand the interrelationship between these if you are not familiar with them yet.  I check pH, temperature, alkalinity and DO in my system together, and break my TAN (Total ammonia nitrogen) count down into ionized and unionized Ammonia.  My system is extablished thus I do not test Nitrites or Nitrates very often, but if the fish behaviour or visible water quality changes, I will check everything.  I do not look at Hardness much, although it can also be a factor in water quality.

 

In terms of the cycling of a system, I think there are some basics that most people need to keep in mind:

1) The bacteria responsible for nitrification and de-nitrification are some of the slowest growing bacteria in nature.

2) The development of Ammonification (the breakdown of more complex nitrogen bonds back to Ammonia), and the two phases of nitrification (Nitrosomonas and Nitrobacter) reacts to spikes in the availability of the chemical they modify.  Thus you need a good source of step 1 chemicals before you will find any trace of step two.  These reactions are temperature and pH dependent, but can take as long as 40 days in suitable environments.  It is not advisable to try cycling a system when you are still trying to get the pH stable or if the temperature is very low.  Things will just take that much longer.  The pH should be in a range of 6.5 to 7.5, and the temperature is better above 65 degrees F if you are in a hurry.

3) any distruption in the flow of ammonia into the system will result in the eventual die-off of the bacterial cultures.  A baseline input of Ammonia must take place daily for the system to remain optimal.  This input can be sourced from fish or the breakdown of solids and old plant material in the system, but some flow of ammonia is vital.

4) just because you cycled on 4 fish, does not mean the system can take 40 now.  Each cycled system is a balance of water flow rates, filter size, media type and current nutrient loading.  Remember the slow-growing bacteria - if the nutrient input has been from 4 fish over an extended period of time, the bacterial cultures will adapt to that.  Same principle as worms in the bed.  You can toss in a million but the end population will match the nutrient supply.  If you cycled on a small fish population and want to increase your fish load, do it gradually.

5) the nitrification process is aerobic.  If your system has been down for more than 12 hours, worry, and if it has been down more than 24, you may want to consider your cultures to be in serious trouble.  Anaerobic respiration may now start surfacing in the system and you may have a disaster in waiting if you just fire it up as is.  Consider the nitrification capacity of your unit to be compromised and check water quality very carefully for a while.  If your DO plummets and / or ammonia and nitrite build up, you may just have to cycle again. 

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Good Points

And these reminders must be repeated often

Ditto!  Bravo, Kobus
It has been brought to my mind that I have been using the soil bacteria references in my nitrification comments (Thanks to Rebecca Branham for spotting that one).  My training references out of that period of my life was all terrestrial - the bacteria responsible for transforming nitrite to nitrate in marine and fresh water environments are Nitrospiras, not Nitrobacter.

Hi kobus,

Thanks for detailing all this AP fact and do's and don'ts. I am not convinced, from some of the information on nitrifying bacteria, that the jury's fully out. I think that little is presently know and as time goes along I'm sure more will be revealed. BTW i just love your emoticon Sylvia!

Re: Nitrospira vs Nitrobacter.  Dr. Wilson Lennard actually corrected me on that when he reviewed parts of my book and said just the opposite...that they are Nitrobacter in AP systems.  Are you sure?  Good thing I'm in the process of a final review of the copy edits now!  (I did that emoticon just for you, Harold!)

I think a lot of us can't access more than the 4 basic ones (emoticons) that show at the bottom, when I click on the more link it doesn't work.

 

 

Sylvia, I think it was always assumed for a very long time that it was nitrobacter responsible for the conversion of nitrite to nitrate but there have been some studies done that seem to suggest that nitrospira and nitrospira like bacteria seem to be doing it in the freshwater aquarium that were tested.

 

Here is a link to a paper on it.

Nitrifying Bacteria

 

Hi Sylvia,

 

I read many conflicting articles on the subject and now I've decided to wait a little until a clearer picture emerges.

Sylvia Bernstein said:

Re: Nitrospira vs Nitrobacter.  Dr. Wilson Lennard actually corrected me on that when he reviewed parts of my book and said just the opposite...that they are Nitrobacter in AP systems.  Are you sure?  Good thing I'm in the process of a final review of the copy edits now!  (I did that emoticon just for you, Harold!)

Sylvia, you can download the original paper by Hovanec from here... http://aem.asm.org/cgi/content/full/64/1/258 ... or directly from... http://aem.asm.org/cgi/reprint/64/1/258

 

There's also a list of references included in the article I wrote on the subject for BYAP mag #5.... email me if you want the whole article and list of references...

 

Here's a couple of other references...

 

A paper by Altmann... http://www.ncbi.nlm.nih.gov/pubmed/12919415?dopt=Abstract

 

A paper by Daims ... http://aem.asm.org/cgi/content/full/67/11/5273

 

A paper by Kim DJ... http://www.ncbi.nlm.nih.gov/pubmed/15927463?dopt=Abstract

 

And some other links... http://www.microbial-ecology.net/googlesearch.asp?cx=01204887656811...

 


Sylvia Bernstein said:

Re: Nitrospira vs Nitrobacter.  Dr. Wilson Lennard actually corrected me on that when he reviewed parts of my book and said just the opposite...that they are Nitrobacter in AP systems.  Are you sure?  Good thing I'm in the process of a final review of the copy edits now!  (I did that emoticon just for you, Harold!)
Beautiful!  Thanks for all the great resources and for setting the record straight!

One to chalk up to "go back to the basics every now and then".  When I studied these aspects of ecology, the discoveries on Nitrospira were barely made - first in the marine setting and then in the freshwater environment too.  None of my text books are modern enough to have reflected the changes.  

 

So which one are you going to go for in your book now? Perhaps to confuse things, there could be a mix, Nitrobacter or Nitrospira, based on the type of cycling you use - perhaps a gradient of Nitrobacter to Nitrospira depending on the degree of submersion with -bacter dominating drier systems and -spira more likely to be in wetter systems?

Ack!  I'm getting a headache....

I'm going to read through the stuff that Rupe sent then try to figure out a way to represent this that will be correct and relevant, but also not overwhelm anyone with science (not that I"m capable of doing that anyway ).  The book is geared at step by step instructions for the home gardener who probably only barely need to know these finer details.  

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