RE: [Killietalk] filter

[Wright Huntley <whuntley at verizon_net>]

Chris,

Chris <cgraseck at optonline_net> wrote:

> Ugg!  First ammonia is not toxic, now nitrate is not toxic at 100s of
> ppms!

I don't know who said ammonia wasn't toxic. It hurts fish at levels of a 
few parts per *billion*. 6-8 ppb is enough to permanently damage gills 
of very young fish. That is well documented in the aquaculture 
literature. [e.g., Burrows, 1964 on salmon]

Ammonium, OTOH is pretty harmless at a few ppm. The amount of which of 
them is present is dependent on temperature and pH. There is essentially 
no ammonia at 20C and pH below 6.5.  At pH=9.4, it is about 50-50 
ammonia and ammonium.

Rule of thumb to remember: The fraction as ammonia at pH of 7 will be 70 
times higher if at a pH of 9. [10X as high at pH of 8.]

> Either my aquarium education is full of hearsay or I'm getting old.
> Maybe both.  I do have to say that I've read many observations of fish
> and invertebrate behavior changing with respect to nitrate
> concentration.  40 ppms sticks in my mind as being a point where many
> Tanganyikans will stop spawning.  I realize that reefing is a different
> story but I'm sure my reef would not look good with 100s of ppms of
> nitrate floating around.

I know the reef folks have a real fear of nitrates, but I don't know the 
mechanism or what it does to inverts. Nitrate certainly behaves 
differently in salt water, for that's why protein skimmers can work 
there, to remove it, and don't work in fresh.

Mostly, AFAIK, the problem with Tanganicans and similar fish is the high 
pH of their environment makes too much of the ammonium convert to 
ammonia and they can suffer mightily from that. Lack of plants can make 
the situation much more unstable than with normal planted tanks, and the 
high metabolic rate of fish like *Lamp. tanganicus* and their big 
appetites make them a serious problem to keep.

[I had never heard the 40 ppm keeps fish from spawning argument, nor had 
I ever read any credible descriptions of behaviour change in high nitrates.]

Spotte, in _Fish and Invertebrate Culture_, 1970, flatly states that 
"There is no conclusive evidence that nitrate or phosphate is directly 
toxic to aquatic animals." [p. 50]

At the endpoint of "cycling" it is very rare for nitrate to go much 
above 20 ppm. The situations I'm aware of were from overdosing of 
fertilizers, like KNO3, and the elevated levels didn't seem to cause any 
problems with the fish, as long as no denitrifying factors (like old 
carbon filters) were present to produce nitrite or ammonia. Baensch and 
Riehl [1987] advise avoiding levels above 150ppm of nitrate as the 
denitrification can be encouraged. IDK how much I trust them, though, 
for they also claim plants can't use ammonia and must have nitrate for 
growth. Sheesh!

Wright

--
Wright Huntley - Rt. 001 Box K36, Bishop CA 93514 - whuntley at verizon_net
                    760 872-3995

        Eschew obfuscation and bloviation!



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