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chrisfoerst
12-02-2011, 09:58 AM
I am working with a group of 5th graders with two aquaponic systems. All of the levels are fine except for the nitrates which are. At 160 ppm. Is this dangerous? The kids have been checking the levels every day and I would like to give them some reasons for the steady climb in nitrates. Thanks!

foodchain
12-02-2011, 10:17 AM
Can you tell us all a little more about your setup/system? Stocking densities, gallons(volume) to Grow Bed(sq ft or inches)?
If your nitrates peaked suddenly, what has been going on with you ammonia readings? Did you recently change anything?

chrisfoerst
12-02-2011, 10:37 AM
Tank 1
75 gallons water, 15 med sized fish (but there were 20) I have been moving them slowly into the 2nd tank as we cycle it. The tank had a spiked ammonia reading yesterday but is lower again today.
Ph 7.4, amm. 2.0, nitrite .25 ( all pp)
Other tank has 10 fish, Ph 7.4, amm. 0 nitrite 0 ( all pp)
Tank 1 has 55 gallon barrel cut in half with plants. 2nd system is a nft sys with about the same number of plants.
Thanks!

keith_r
12-02-2011, 10:55 AM
how are the plants looking?
while high nitrates do "concern" me to some extent..but most fish are ok until the readings are at 400+ for an extended period (at least that's what my research has led me to believe)....
but fry are more susceptable to problems associated with high nitrates..
don't feed the fish anything in the system that has the am at 2... and don't put any more fish in it until the am drops
if you can get more plants in, (maybe a small raft or two in the ft) or even a tank plant or two will help use up the nitrates, but if you add plants, you should also add aeration if you haven't already

chrisfoerst
12-02-2011, 11:07 AM
The established plants are doing ok but I have had terrible luck at transplanting seedlings. (I used the horticulture cubes and transplanted them in when they were about 2-3 inches tall but almost all of them have died (except the beans and peas) Do you need to protect the seedlings in some way? I have never had success with transplants.

Thanks for the info! We are finishing up the project at the school this coming week. So, I'll have some time to incorporate more plants. Do you mean to aerate the plant roots or the FT?

I appreciate the quick reply!

foodchain
12-02-2011, 11:26 AM
Transplants suck for me too. Gone to direct sowing. Finding if something doesn't want to work for you, better to change approach than try and force it.

keith_r
12-02-2011, 11:46 AM
i haven't done any real transplants in my system, but i took cuttings from basil, oregano, thyme and parsley,, walked out back, cut some branches, walked into the basement and stuck them in the gravel... every one of the cuttings took off.. so "cloning" was pretty easy for the few things i tried..

oh.. and a little while back, my stepdaughter pulled one of her fennel plants out of her dirt garden,, she cut the root off and left it sitting in the yard.. after seeing it there when i came home from work for a few days, i finally brought it inside and stuck it into the gravel, it was kinda dried out looking, but i figured what the heck,, within the past 3 weeks, it has over a half dozen "sprouts", some already over 6"!

chrisfoerst
12-02-2011, 01:10 PM
Good, so direct sowing and cuttings. I will try that as soon as I set up my system at its next location. Thanks!

urbanfarmer
12-02-2011, 07:49 PM
I am working with a group of 5th graders with two aquaponic systems. All of the levels are fine except for the nitrates which are. At 160 ppm. Is this dangerous? The kids have been checking the levels every day and I would like to give them some reasons for the steady climb in nitrates. Thanks!
Nitrate is generally not toxic to fish. Some species may have sensitivity to nitrate, but the majority of commonly cultured fish species do not. The concentration of nitrate you stated is far from remotely dangerous to any adult of a fish species that I can think of. However, the high nitrate concentration can be indicative of an imbalance in your system. You need more plants to remove the nitrates; however, as seedlings grow they absorb more and more nitrate and ammonia.

One other issue with high nitrate is that under certain conditions (DO, pH, concentration of nitrate, maybe even temp) there may be a viable environment for a certain type of bacteria that uses nitrate as a food source and converts it to nitrite. They would of course have to out compete the other bacteria. Needless to say, if you have 500 ppm nitrate and only 10% of that gets converted to nitrite in a given instance, well dead fish could be a reality. However, keep in mind the bacteria that convert the nitrite to nitrate could be present somewhere else in the system entirely; so, it all depends on who, what, where, when, why.

chrisfoerst
12-04-2011, 08:58 PM
Ok, thanks for the input. No matter what, I need to get more plants into the system so that will be my next task.

foodchain
12-05-2011, 05:47 AM
HA.....This is what we all want isn't it? Problem or not, we are all looking to expand on what we can grow next. :) Good Luck.