Backyard Aquaponics
A place to discuss aquaponics

I think nitrates are mostly a problem when combined with low oxygenation...

The studies that refer to any possible affects of nitrates relate primarily to the development of "fry"... and are usually related to contaminated water sources or agricultural run off from fertilisers... i.e sodium and potassium nitrates...

Not the "nitrate" compound forms seen in AP or aquaculture (unless from compounds formed from decomposition of preservative additives in feed)....

Any such "problems" have been shown to occur in situations where overall water quality would be so poor that it would be toxic to fish health from other aspects anyway.

Sorry rupe, I'll stop baiting you.
I never realized the nitrtrate compounds found in AP were different enough. What then is it that builds up in a non ap old school aquarium that will kill the fish? Given that ammonia and nitrite are taken care of by the cannister filter? Why are water changes required?

Actually, I should have been more specific and qualified my post better Kuda...

The studies I referred to related to nitrate uptake and toxicity primarily in pond based aquaculture systems... through concentration from external sources...

And were intended to quantify the level of nitrates required to reach levels of toxicity...

Due to the large volume of pond based systems, and uptake by natural aquatic plants and algae, it isn't normally a problem in such systems....


The nitrate produced through the nitrification of ammonia... as in RAS systems, aquariums and AP systems... is identical... (as indeed it is in pond systems)...

Due to the relatively smaller volume of water, and the recirculating nature of the above systems, nitrate concentration continues to build in such systems to the point of toxicity... unless dealt with...

In RAS systems this is done by various methods incorporated within bio-filtration processes... primarily by off-gassing and/or simulated anaerobic process... as employed also by waste water treatments....

And by routine water changes....

In aquaria, which by nature are very small volumes of water in comparison, the constant recirculation of the water ... or more normally... the complete lack of recirculation of the water... could indeed build toxic levels of nitrate quite quickly... and again the solution applied is routine water changes...

In AP... of course... we use the plants to uptake the nitrates... thus preventing the need to do routine water changes...

Regardless, the levels of nitrate required to reach levels of toxicity are very large... evidence suggests that indeed many fish species can adapt over time to large levels of nitrate exposure, some species better than others...

Small fish stock... fry... are much more susceptible to toxicity...and hatcheries take steps to address the problem... again usually through routine water changes..

And again, I suggest that, just as in aquaria, if the levels in a RAS system ... or AP... were to approach the levels of toxicity required to harm fish... then your bio-filtration and water management practices would prevent other more significant and fatal consequences to your fish stock before any affect from nitrates...

Sorry, that last sentance should read...

"then your bio-filtration and water management practices would present other more significant and fatal consequences to your fish stock before any affect from nitrates..."

In ap, I expect this summation to be probable. Thanks for clearing that up. So if we were to remove plants as suggested above somewhere, nitrate poisoning would eventually ensue. However while any plants remain in the system nitrate toxicity is nigh on impossible.

Eventually... if you treated your system like an aquarium, but without doing water changes..

Janet had a situation some time ago where she had limited plants, no water changes.. and pushed her nitrates to about 1000 (calculated) from memory... leading her to experiment with the RSG filter... an anaerobic "denitrification" conversion of nitrates to N02 which was off-gassed...

I'm in process of constructing my Bakki Shower for the 6000L trout system... which currently doesn't have any growbed filtration....

One of the benefits of the Bakki shower is that they are particularly good at nitrate conversion and off-gassing... so much so that many of the Koi keepers now use them as the SOLE means of bio-filtration....

Well dont keep it to yourself photos you know we love photos

Hope to have everything I need this weekend F&F... photos will of course be posted...

And I need to do something... threw another 200 trout in there last weekend...

Can't keep doing water changes...

So if its not the salt, and not the nitrate and not the pruning and not the aeration...

WTF KILLED MY FISH????

Not what Kirk, but rather who????


Thats the problem, could be soooo many different things, spray drift from a neighbour?

I missed the bit where it was found salt was not the problem?

If the salt's from an inland lake, it could have a substantially different ionic composition to seawater- the manufacturer should have an analysis of the salt which you could compare to seawater.

I have used inland salt lake excusivly, I am only curious becuase it was said the salt was an unbranded generic salt?

I'm with EB, either spray drift or sabotage, has been known to happen, is it to late to test the water DP, take some to dept of ag