nitrite and nitrate levels

[jillswindoll]

My system is finally completely up and running! I had about 60 koi in a 1000-gallon tank for several months and for the majority of that time I did not have a pump running. The water was green (no surprise there!) but about half of the surface was covered with water hyacinth and the fish seemed very happy. My ammonia, nitrite, and nitrate levels have always been zero. Then I added some bacteria that I got from Paula Speraneo of S&S Aquafarm.

I finally got a timer and I ran the system through a 8'x4'x1' bed with no plants in it. The algae started to bum me out so I decided to tackle that problem before I added plants. I removed all of the water hyacinth, covered the pond with black landscape fabric and stopped feeding the fish for four days. I added a small additional filter to add a bit more air and hopefully get rid of some of the green crud. Water chemistry looked good, too.

It worked! I had such crystal clear water that all I wanted to do was sit and look at it all day!! I was so proud!

I added about fifty lettuce plants last week and they seem happy. The problem now is that now, for the first time ever, I have nitrite readings of 0.25ppm and nitrate levels of 5.0ppm. I lost two fish this weekend!

Before I discovered this problem I was actually worried about not having enough fish since my experience with these fish has always been zero readings of ammonia, nitrite, and nitrate. What gives??? My first thought was that now that the algae and water hyacinth are gone there isn't enough plant life to take up the waste products. But if that was the case don't you think my lettuce would be growing like crazy instead of just seeming happy?

Thanks!







It worked

[Ravnis]

Sorry about your fish!

The water hyacinth and possible the algae were "eating the ammonia". Nitrates of 5 is ok and the nitrite of 0.25 should not be that much of a problem.

This ia a guess...with the ammonia going straight to the plants you may not have set up the general conversions of ammonia to nitrite , nitrite to nitrate. Water plants can use the ammonia directly and literally starve the nitrifying bacteria. The fact that you did not have nitrate levels before and now are seeing some is more evidence that the cycle is establishing and fast. I am running minnows with nitrates in the 30 -40 range and they are currently doing fine after the stress of coming from the bait shop to there new home.

A wise man on this board said something to the effect of... do changes in small steps and slowly. The sudden lack of filtering, shade, loss of algae(they shade the beneficial bacteria from the sun) might have caused a temporary imbalance that led to the deaths. Again this is still a guess.

[Outbackozzie]

+1 for above, and was there aeration to the pond while the cover was on? If not I would blame lack of oxygen for the deaths.

[Jonathan Dyer]

pH Guys pH what is your pH readings? If the fabric was on the water stopping the fish from getting air from the surface I would agree with Ozzie. 60 Koi in 4500L of water there should never be a problem with o2 levels even without a pump unless they couldnt gasp for air at the surface. Test your pH, much more important than your low readings of nitrogen. Your system would have cycled without a dout the bacteria would be growing on the plant roots, walls of the tank, and any other place suitable. I do recomend adding Salt to your system say 9lb, but that is English pounds is there a difference between US and England weights.

[GaryD]

Hi,



....I would blame lack of oxygen for the deaths

Me too!

Gary

[jillswindoll]

Thanks for your replies! I had no idea that the water plants could use the ammonia directly!

pH is fine, it has ranged between 7.2 and 7.6 over the past six months.

As for oxygen, the water level is about six inches below the landscape fabric and it rests on a web of fishing line I made to keep the fabric off the surface of the water. There is a place where there is no cover, where the water returns to the tank, that is about 2ft^2 (about .2 square meters). I don't know if this is sufficient. Let me know what you think...I would rather have pea soup for water than dead fish!!

If the bacteria were growing all over the plant roots and I removed them all at once then I might have really put a dent in the bacteria population. I have a LITTLE more of that culture left that I can add in there this morning.

You know, I was thinking of taking the remaining culture (enough for ~1/4 of the volume in my tank) and putting it in a larger container with some pond water and leaving it on the shelf to multiply...that should work, right??

I will add salt as well. I have read that it is very good for the koi to add salt to the water but I always wondered about adding salt to an aquaponics system. What effect will it have on the plants/roots in the growbed?

You guys rock! Thanks for all of the great advice!

[Outbackozzie]

up to 3kg of salt per 1000 litres is fine. All plants except for strawberries seem to do ok.

[Jonathan Dyer]

As for oxygen, the water level is about six inches below the landscape fabric and it rests on a web of fishing line I made to keep the fabric off the surface of the water. There is a place where there is no cover, where the water returns to the tank, that is about 2ft^2 (about .2 square meters). I don't know if this is sufficient. Let me know what you think...I would rather have pea soup for water than dead fish!!

I don’t see an issue whatsoever. Your fish had ample access to air, remember Koi and Goldfish are able to breathe large amounts of air from the atmosphere I would find it hard to believe that they died due to lack of oxygen as your return line is also adding additional oxygen as well.


If the bacteria were growing all over the plant roots and I removed them all at once then I might have really put a dent in the bacteria population. I have a LITTLE more of that culture left that I can add in there this morning.

I wouldn’t be to concerned about this as there will be enough bacteria elsewhere on the walls, bottom gravel if you have any, rotting debris on the bottom but, 60 fish in 1000 gallons really isn’t enough to have high readings of nitrogen anyway I have over 100 Koi in 500 gallons with ammonia/nitrite readings Zero and nitrate around 40ppm (I still have to add more fertiliser to get good plant growth). You experienced the same sort of thing 60 fish even at 12” long per 1000 gallons is nothing (how large are your fish anyway?) the dilution rate and waste they produce is not much at all, you will have an active bacteria population that converts waste very quickly you just don’t have enough waste to get much of a reading, although your water Hyacinth would have been supporting a large percentage of the bacteria so there could have been an issue. As for your recent readings of nitrite 0.25ppm and nitrate levels of 5.0ppm the algae and hyacinth is able to uptake ammonia directly from the water as discussed, as do most other water plants (duckweed, azolla) they would have had a large effect on the uptake of nutrients but, you have done some major changes to your system in a short time this alone will have put things out of balance and needs time to recover causing excessive stress on your fish. During these times of stress contrary to what people say or recommend, feed is very important sometimes during periods of stress fish go off there food and adding more food can cause poorer water quality = more stress but is a very poorly managed fish tank if this be the case; but if one sees that the fish does not go off there food I would never stop feeding especially for a Koi it can be detrimental, I would even give a sick fish just a bit of food even if they wouldn’t eat it, fish husbandry is about 90% observation. Perhaps you lost those fish due to excessive stress and lack of food; remember Koi don’t have a stomach as such so they need little bits of food often; I feed my Koi around 5 times a day.


You know, I was thinking of taking the remaining culture (enough for ~1/4 of the volume in my tank) and putting it in a larger container with some pond water and leaving it on the shelf to multiply...that should work, right??


Generally no and not necessary. Doing this will not achieve anything, for one the bacteria need lots of oxygen so continuous aeration would be needed secondly the bacteria needs something to adhere in order to colonise gravel, sand, plant roots are classic examples and the more surface area the larger the colony of bacteria will be, thirdly the bacteria needs a source of ammonium to start the cycling process adding a small amount of urea 1teaspoon per week would be needed. So therefore, doing this would not achieve much I would even say that most of the bacteria would die anyway unless of course you added air, bio-filter and urea, just add the water to your tank it wont hurt much.


I will add salt as well. I have read that it is very good for the koi to add salt to the water but I always wondered about adding salt to an aquaponics system. What effect will it have on the plants/roots in the growbed?

9 pounds of Salt in 1000gallons should not affect your plants at all, 9 pounds would be perfect for Koi but I would never go much over 18 pounds at this rate plants like strawberries and beans may have adverse affects as well as causing a bit more osmotic imbalance to your Koi.

[jillswindoll]

Can I use Kosher salt or should I use special aquarium salt?

I guess I did make a lot of big changes in a short period of time...

[Jonathan Dyer]

Honestly it doesn’t really matter too much what type of salt you do use. But I have used specially designed ‘Aquarium Salts’ for Goldfish and Koi in the past, how much better it is than common table salt I don’t know but according to the labeling it should have an edge. Kosher salt is and will work just as good, I don’t mind sea salt as it has other minerals and trace elements as well as increasing hardness levels of the water, I have used iodised salt with no ill effects many times. At the end of the day I think any type of salt is better than no salt in a system the health benefits to your fish is tremendous, I have never lost a fist to date and the salt I run (1000ppm maintenance level) in my system is I think the reason why.

[jillswindoll]

Should I add it all at once or over several days?

[Jonathan Dyer]

Your best bet is adding it over 6Hrs. Say 1.5lbs/hr disolved in boiling water adding it slowley where it can be mixed through your tank like the return line from the grow bed. If you can not do this add the entire lot disolved in say 3 gallons of boiling water and apply evenly around the entire tank make sure it is not too hot for the fish. There are no guidelines when adding salt but if I was to add salt it would be within the same day, its just the slower you add the salt to your system the more acclimitised your fish become rather than a sudden spike; but really 9lbs or 9.5lbs is not much salt anyway around 1000ppm.

[fishfood]

Just my 2 cents worth i allways thought you needed the change of salinity as quickley as possable the fish can take it the bugs need time to acclimatise
i allways [over two years and no problem] dumped the salt up to 4 kg per 1000 litre straight in the fish tank as far as salt goes the only plants i have ever lost to salt over 2 years was strawberrys

[Outbackozzie]

Iodised salt is not recommended for larger doses however.

Normal pool or lake salt is fine.

+1 for sudden salt concentration changes for sick fish, but if just topping up the salt level it can be done slowly. I usually just dump the whole lot in the sump at once.

[djs-sa]

when i've used salt i dump it straight in and it doesnt desolve straight away but in a few hours it desolves completely

[Hamish]

when i've used salt i dump it straight in and it doesnt desolve straight away but in a few hours it desolves completely
I have found this too - if you dump it all in at once it disolves over a few hours. It sits in a layer on the bottom of the tank while it disolves. I dont salt because it was killing my strawberries - seriously think I will remove the straberries soon - they just dont seem to like salt so best put them in the ground and use the spaces to grow other things :D

[Outbackozzie]

Strawberries, Fish and AP dont mix long term.

My system got 20kg of salt added all at once today :eek:

[Hamish]

Agreed - I run no salt now and the strawberries are happy. When I was running salt the strawberries were very sick.

[Outbackozzie]

I prefer happy fish, and sick strawberries :)

[Murray]

OBO, How many ltrs of water in your system for 20KG of salt ?

[Dufflight]

I dropped in 50kgs the other day. And am thinking of another 25. Will have to get a salt tester later.

[Hamish]

No salt in my system and no lost fish other than the 3 I lost when I first got them - so I guess they are happy. If I notice them getting sick I will add some salt.

[Finn]

I am curious as to why you would add salt to a fresh water fish tank?


"The body fluids of a freshwater (fish) contain more dissolved salts and ions than the surrounding water. As a result of this imbalance there is a constant influx of water into its body and a loss of salts and ions from the blood outwards... a fish has to rid its body of excess inflowing water by constantly excreting a weak solution of urine. Fresh-water fish can urinate approximately 30 per cent of their body mass each day."

"The reverse situation exists in marine fish; the environment contains more dissolved salts and ions than the fish's body so there is a net movement of water out of the fish's body into the stronger sea-water. To replace this constant loss of water, marine fish drink sea-water and excrete the excess salts. Special cells in the gills called chloride excretory cells are involved in this process."

"Clearly, any interference to the fish's osmoregulatory systems, either fresh water or marine, would quickly prove fatal! Fresh water fish would rapidly accumulate water (a typical sign seen in dropsy), while marine fish would dehydrate."
-Osmoregulation and fish health http://www.fishdoc.co.uk/water/osmoregulation.htm(thanks for the link Gary)

So wouldn't adding salt make fresh water fish more susceptable to dropsy? Since more than a couple of people are adding salt and their fish are doing well, I am obviously missing something.:o

Finn

[Murray]

I think the answer lies in the fact that most Australian native fresh water fish adapt readily to brackish water because the switch from brackish to fresh and back again happens in their natural environment.
I guess over the millenniums they have adapted to their unique environment.

I do wonder at the amount of salt some claim to add to their fish tanks.

I feel some of the claimed measurements could be affected by the liberal application of a fermented drink made from the leaves of the hop plant.:D Much bending of the elbow prior to adding the salt or making the post . :D Another peculiarity of some native Australian species.

[Dufflight]

I like that. Hopefully over the years we too will adapt to the drink you talk about.:D And like our fishy friends we will be able to urinate 30% of our bodies.:)