Nitrate build up

[Chandara Khan]

Hello everyone! I need your help. Could you tell me from your understanding or your experience about the duration or days that nitrate occurs firstly in all kinds of Aquaponics systems. Here are some results after testing the water in my system: pH 7.1, NH4 0.5mg/L , Nitrite(NO2) 0.5mg/L ,  PO4 between 0.5 &1mg/L and Temperature is 29C. My nitrate test kit is has no effect on the tested water. I mean there is no result for nitrate; maybe the kit is out of date. Well have you got any mathematical ways in calculate the amount of nitrate in my system? My system is around 20 days old.

[TCLynx]

take a sample of the water to an aquarium shop or pet store with an aquarium section, they can usually do a water test for you so you can find out if your test kit has gone bad.  It can happen.  However, if the system is only 20 days old and conditions not perfect, it is possible that there are not much in the way of nitrates yet.  To figure out how much nitrates you have using math, we would need to know exactly how much ammonia has been generated over time as well as some way to know if any nitrates have been removed by plants or denitrification or water changes.

 

I wouldn't worry to much about nitrates yet but it would be good for you to sort out if your test kit has gone bad.  The API nitrate test should at least turn the water yellow even if the nitrates are 0.

[Jonathan Farrand]

Nitrate is the last level of the nitrogen cycle. First ammonia and then nitrite and then nitrate. It is true plants want nitrate and it is also true the first two lower levels of nitrate are very toxic for fish over extended periods of time. If you are not seeing signs of nitrate your system has most likely not reached that level of the nitrogen cycle yet or your system is already perfectly balanced and comsuming all of that nitrogen in whatever form your system is currently producing.  Early on in cycling a system it takes time for the ammonia nitrogen to covert to nitrite nitrogen(both unhealthy for fish) and then finally to the less toxic for fish nitrate nitrogen. By the time your cycle gets to the final stage hopefully your plants would take over from there. By the look of your plants and comparing to my three week old system things look good. If you see different behavior in your fish be concerned with possible ammonia or nitrite poisoning and you should give a slight water change to fix the problem.     Hopefully helpful and short story: Your system may be to young to show traces of nitrate.

[Francois Lemmer]

Hi TCLynx

The advice you give to questions....worth its weight in gold...

Please carry on with your good advice to the community...us...me

Very good advice and why’s

Really helps allot

TCLynx said:

take a sample of the water to an aquarium shop or pet store with an aquarium section, they can usually do a water test for you so you can find out if your test kit has gone bad.  It can happen.  However, if the system is only 20 days old and conditions not perfect, it is possible that there are not much in the way of nitrates yet.  To figure out how much nitrates you have using math, we would need to know exactly how much ammonia has been generated over time as well as some way to know if any nitrates have been removed by plants or denitrification or water changes.

 

I wouldn't worry to much about nitrates yet but it would be good for you to sort out if your test kit has gone bad.  The API nitrate test should at least turn the water yellow even if the nitrates are 0.

[TCLynx]

[Kobus Jooste]

The Nitrogen cycle runs through quite a few phases, with specific bacteria responsible for the conversion of say NH4 to NO2 and another one to go from NO2 to NO3 and so forth.  These bacteria are of the slowest growing bacteria in the natural world - responding to elevated levels of their chemical of choice before blooming.  The attached graph is from aquaculture, but shows how you really need a peak in one nitrogen phase to trigger the development of the bacteria that breaks it down.  If you have an interruption in your bio-fiilter, the population will die back again, thus you always need some ammonia coming in to keep the whole colony growing and thriving.  Starting with a small amount of ammonia may also not trigger the wholescale bloom of the other bacterial phases - you mention under 1 mg/l of the NH4 and NO2, while I have higher required levels in my head for getting the system cycling properly - above 2 mg/l NH4, but I am not sure how accurate that is. 

 

 

[TCLynx]

I've managed to cycle up several systems without ever dosing beyond 2 ppm of ammonia.  1 ppm should be enough but it can be hard to get exactly that when dosing using hummonia (aged pee) so we usually aim to dose between 1 and 2 ppm.  Once we can dose to that level and have both ammonia and nitrite back to 0 within 24 hours, we call it cycled and add fish (or keep dosing until the day before we can add fish.)

 

Now I've found that in a mature system (that has a good load of solids slowly breaking down in the grow beds) letting the system go for a time without fish doesn't cause it to run out of nutrients right away.  And it seems that the solids slowly breaking down are providing a slow release of ammonia to help keep the bio-filter active.  Now it is likely that the bio filter bacteria colony will die back a fair bit with only a small amount of ammonia daily so when adding fish back in one must watch for spikes and ramp the feed up slowly to allow the bacteria population to build back up but as long as the bacteria colony didn't die off completely, this goes much quicker than initial cycle up of a new system.