Aquaponic Gardening

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At some point in every system, there is a bit of a wobble in the nitrification cycle - perhaps you have been over feeding, have not been checking on the system regularly or whatever.  What I have noticed as a trend in many of the discussions in the general forum is that people appear to be very jumpy about ammonia and tend to go into panic mode at concentrations that I typically ignore in my system.


Your choice of fish is important here, I know.  Mozambique tilapia are tough bastards alright - reason enough for me to recommend them to anyone that is in an area where they can be legally and responsibly owned.  In a past "scare", I had nitrites touching 7 ppm and ammonia over 5 ppm.  I did not lose a fish and I did not make even a partial water change.  I was worried, but I had a couple of data sets at my disposal which I used as a "Plan B" generator in the situation.  Water was a premium to me, not only because of all of the nutrients already in the AP system, but because of the drought I'm working in.  Water loss was therefore not a great idea for me.  What I did have was the tolerances for the species (water quality) from a reliable source - aquaculture publications.  I also have a decent knowledge of how temperature and pH work together to influence the toxicity of ammonia and nitrite. 


Thus plan B was keep the temp down, the DO levels high, pin the pH to 6.5 and slow the feeding rate right down.  It took a full 20 days before the readings were such that I thought the system was good to go again, but the moral of the story for me was that there were more than one way to get a system out of a tail spin, and that it is not always necessary to go for the parachute.  I'd like to know your thoughts on this concept - also what you know about your fish's tolerance levels - do you use tolerance data or caution as your guide to water management? 

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Personally, I tend to watch my fish.  I've got catfish with sensitive skin and I've seen them start showing signs of going off the feed and start scraping on things when the ammonia starts climbing near 1.  Of course this definitely varies by fish size/age.  The small fingerlings seem to survive much worse conditions than the 6+ inch (15cm) long ones.


Of course as Kobus says, look up some charts to see what the temperature and pH do to the ammonia.  If the pH is below 7 you can get away with alot more in the way of ammonia than if you are struggling with a new system cycle up with well water over 8.  (Course this can be a catch 22 since the ammonia is supposed to convert better at high pH but it is also more toxic at the high pH.)


Anyway, I agree that if you can resist the water changes (have tough fish) NOT changing the water will actually help things cycle quicker (provided you didn't send the ammonia off the chart since ammonia over 8 ppm can inhibit the bacteria too.) 


And one of the more common causes of the sudden (not during initial cycle up) ammonia spikes is a drop in the pH.  This is why I remind people to keep a close watch on their system pH even after the daily testing of cycle up is past.  Test pH a couple times a week if you don't have a buffer in the system and weekly if you have some experience in what your buffer will do in the system.  Luckily the pH crash ammonia spike tends to happen when the pH goes too low so the ammonia won't be as toxic, however you must bring the pH up to get things working again so stop feeding and hope the water isn't too warm.  And this might be a situation where some one doing timed flood and drain might be helped by going to constant flood till the situation clears up.


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