KCl use in Aquaponics

[Eric Warwick]

This is a thread jack from the comment section of http://community.theaquaponicsource.com/group/artificiallighting . Here's the transcript from the sicko's Jon and Vlad, along with TCLynx and myself. (Read from the bottom.)

Vlad: TC, just out of curiosity...why do you say "in a pinch"? Don't folks salt their systems with NaCl for the chloride ions (tonic for the fish, mitigating nitrite poisoning blabla...)? Potassium chloride seems like a grand way to add K for the plants and provide some chloride ions for the fish at the same time...Is there any reason you know of that this would not be so?

(Jon, cue the music and put your ski mask on ...

TCLynx: Potassium Chloride can work to provide potassium in  a pinch but for me if the pH is fine, I'll usually use some seaweed extract to also get trace elements along with the potassium.As to the tomatoes and flowering.  Toms where I live are a spring and fall crop since summer is too darn hot.  Now we usually don't get the super extreme heat but since I'm in a humid climate it doesn't usually cool off enough at night for good flower/fruit set during the extreme heat of summer.  If you can keep the plant alive and well through the extreme heat, then once the temps come down a bit and you can get the right differential between night and day you should hopefully start seeing some tomato production.

Me: Jon, yes you could, but it's not as efficient as a K buffer. Ultimately, if your pH is good, then your nutrients are going to be absorbed better, which equals less deficiencies. I think, ultimately, if you're making your own nutrient solutions (hydroponic) then KCl would work. I guess it's cheaper to use Calcium Bicarbonate to buffer as well. Anyways, whatever works. 

            Comment by Jon Parr yesterday

Excellent. On the potassium issue, could one use potassium chloride? It certainly is cheap, just paid $12 for 50 lbs, and it's 51% K. Borderline threadjacking, here

Vlad: TC, just out of curiosity...why do you say "in a pinch"? Don't folks salt their systems with NaCl for the chloride ions (tonic for the fish, mitigating nitrite poisoning blabla...)? Potassium chloride seems like a grand way to add K for the plants and provide some chloride ions for the fish at the same time...Is there any reason you know of that this would not be so?

(Jon, cue the music and put your ski mask on ...

TCLynx: Potassium Chloride can work to provide potassium in  a pinch but for me if the pH is fine, I'll usually use some seaweed extract to also get trace elements along with the potassium.As to the tomatoes and flowering.  Toms where I live are a spring and fall crop since summer is too darn hot.  Now we usually don't get the super extreme heat but since I'm in a humid climate it doesn't usually cool off enough at night for good flower/fruit set during the extreme heat of summer.  If you can keep the plant alive and well through the extreme heat, then once the temps come down a bit and you can get the right differential between night and day you should hopefully start seeing some tomato production.

Me: Jon, yes you could, but it's not as efficient as a K buffer. Ultimately, if your pH is good, then your nutrients are going to be absorbed better, which equals less deficiencies. I think, ultimately, if you're making your own nutrient solutions (hydroponic) then KCl would work. I guess it's cheaper to use Calcium Bicarbonate to buffer as well. Anyways, whatever works. 

[Jon Parr]

Excellent. On the potassium issue, could one use potassium chloride? It certainly is cheap, just paid $12 for 50 lbs, and it's 51% K. Borderline threadjacking, here

[TCLynx]

FYI, for nitrite mitigation I don't think you actually have to salt all that high.  I don't know if there is any way to link to the article in BYAP mag but in the first issue there is an article that gives the math stating how much salt is needed per ppm of nitrite and I think it was something like 17 ppm of salt per some amount of nitrite.  But seeing as 1 ppt of salt is generally not detrimental to any plants or fish, it is an easy amount to salt to for protecting from nitrite.

I know when I transport or move fish I've been salting the transport water to 3ppt and after the move this summer we didn't lose any fish in the immediate 2 weeks following the move (aside from one Bluegill that jumped.)

[Vlad Jovanovic]

Cool. Thanks TC. In that case it really probably isn't even necessary to adjust weight when using KCl, eh? I saw in that study they used like 250ppm (mg/L) chloride (so like 0.5ppt salt) for crazy nitrite numbers like 10 and even 20ppm...Looks like channel cats are real nitrite sensitive huh?

I dug up that issue on my hard drive. If posting the tidbit on nitrite here, for people to see, presents some type of problem, let me know and I'll delete it.

BYAP Magazine, Issue 1 Pg. 29

Nitrite
At rates as low as 0.5ppm, nitrite can
be harmful to your fish. Nitrite affects
the ability of the fish’s gills to efficiently
transfer oxygen to bloodstream. This
issue becomes more significant at lower
oxygen saturation levels, for example
when the temperature of the water is
high.
It has been shown that the addition of
chloride will reduce the absorption of
nitrite across a fish’s gills and therefore
assist in reducing the toxicity of nitrite.
Salt (sodium chloride) added at a rate of
17ppm (17 grams per 1000 litres) for each
ppm of nitrite will reduce the effect of
nitrite. Some people keep 1 gram per litre
of salt in their systems on a permanent
basis for therapeutic purposes, as a stress
reliever and aid to disease recovery. Of
course this level is more than enough
to also complete the function of nitrite
toxicity reduction.
As salt will not entirely eliminate the
harmful effects of nitrite and at higher
concentrations can also affect the health

of some plants, the preferred method
for guarding against nitrite poisoning
is to ensure that cycling is properly
completed and nitrite spikes are avoided
by maintaining a balanced system. For
example, avoid the temptation to make
sudden significant increases in the rate
of feeding. Also, ensure that preventative
measures, such as water changes, are
employed to address the short term
inability of beneficial bacteria to process
the increased production of nitrite (and
ammonia) caused by any significant
increase in fish population density.