Ravnis

How critical is ph for fish growth

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A question was raised as to how pH effects fish growth.  While the answer is likely species dependent,  here is one study that shows growth to be similar at pH's many have argued are too low to grow fish at.  I always feel it is good to question preconceived notions whether others, or our own.

 

 

 http://www.sciencedirect.com/science/article/pii/0044848677901569

 

Anyone else has links to other studies, feel free to post them here.

Edited by Ravnis (see edit history)
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Hi Ravnis,

 

That's interesting......particularly given the choice of Brown trout for the study.   The lower the pH, the higher ammonia levels that can be safely endured by the fish.   I wonder if 48 days was sufficient to determine that the fish would remain in good health with a longer term exposure to such low pH.

 

I'd also be interested to know how the production system was configured.

 

I always feel it is good to question preconceived notions whether others, or our own.

 

 

I agree.....but not all inaccurate information comes from pre-conceived notions.   Even if this study is accurate and broadly applicable, it's probably a bit too early to get out the acid.  Perceptions around higher pH levels have their origins in the work of reputable aquaculture professionals.  Also, I think it's fair to say that aquaculture is still evolving as a discipline.  New things are being learned all the time.

 

 

Gary

Edited by Gary Donaldson (see edit history)
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All my systems have always run at pH i below 6.4... often around 6.0.... and all my fish have grown successfully, including high densities of rainbow trout

 

If you equate Australian native fish.. to Australian environmental conditions.. which often result in low pH water bodies....  I believe they have evolved accordingly...

 

There has been a notion that Silver Perch grow optimally at a pH > 8.0... but the reality is that is more a reflection of the optimal feed availability of the algael bloom induced pond methodology, and pH basis.... and the microorganisms and feed succession that promotes, rather than a direct pH factor with regards to the fish

Edited by RupertofOZ (see edit history)
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From my studies in algae for biofuels , I learned that the pH of the water will directly influence the type of algae species that becomes dominant.  So that makes a lot of sense to me in that context.

 

I too question whether 48 days is enough.  Also, it seems that growing out adult that aren't reproducing can tolerate wider pH extremes, that breeders.  

 

Interesting side note and may be a consideration at pH lower than 5 is that Aluminum is  considered relatively non-toxic till at a pH below 5.5.  IIRC, other metals change toxicity in relation to pH

Edited by Ravnis (see edit history)
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Loved this was shared... as I mentioned... I was hoping something would be...

 

 

All of the other studies I found in context of Trout in pH below 6 was increased incidents of coughing and gill respiratory function problem.... but apparently these ailmentsdon't sufficiently impact growth?

 

https://www.google.com/?gws_rd=ssl#q=trout+pH+coughing+respiratory

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Ventilation rate increased to either side of neutrality, but significantly fewer respiratory reversals, or "coughs," were observed at pH 6 and a greater number at pH 9 than occurred at pH 7 and 8 or in untested fish. The respiratory-cough response is shown to be pH-dependent in rainbow trout and may therefore not be as reliable an indication of pollutant-caused stress in studies where the experimental pH has not been specified or controlled.

 

So exactly what is this telling us.... that there's a some detrimental effect of fewer "coughs" at a lower pH???..

 

Or just that such a measurement might "not be as reliable an indication of pollutant-caused stress in studies"

Edited by RupertofOZ (see edit history)
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Thanks for pointing this out Ravnis and Rupert. :thumbsu:

 

 

Also, due to the nishikigoi hobby, I do know that the Carp grown in Japan come from an environment in the high 5 to low 6 pH range, but, when kept there, there are visual alterations to the ornamental fish's color mutations resorting to devaluation of the breeder's crop... thus, nishikigoi breeders try to maintain a pH around 7.0~8.3. Although, other than what I read from nishikigoi breeders, I am unaware of any study that validates this.

Edited by crsublette (see edit history)

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What is it... 3 to 4 months for trout fingerlings to reach plate size of around 500 grams?

I think it's a little longer.

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My ph is 8.4 to 8.5 in my ponds. It doesn't vary during the day due to the immensely high buffer of 350 mg/l of alkalinty. I have a heck of a time dropping the ph in my swim spa that uses the same water. As soon as I get the ph down in the range that works the best for chlorination with muriatic acid, it bounces back.

I have no problem growing fast growing large fish in my high ph, high alkalinity, very hard water.

I'd post pics but think everyone has seen them.

Largest BG so far: 1lb. 8. 1/2 oz.

Largest YP: 2 lbs. 13 oz. (largest ever recorded yellow perch in my state)

Largest Brook Trout: 6 lbs. 10 oz.

Largest Brown Trout: 12 lbs. +

Largest Rainbow Trout: 9 lbs. 9 oz.

Largest Smallmouth 3 lbs. ? *

Largest Largemouth 6 lbs. *

* Didn't keep them long enough to grow them larger.

Edited by Cecil (see edit history)
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Yeah, given the trout life cycle from fingerling to plate size is 3~4 months (92~122 days), or a little longer....

 

 

Makes me wonder if a 48 day study is a sufficient window to gain a proper judge of a Trout's overall growth from fingerling to plate size...

 

Don't know why the study ended at 48 days.

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Hardly scientific but my murray cod at home go's of the food when pH drops below 5.8. while they don't mind the 8.5 they face now and then if I overdose with base.

 

Most aquaculture species are tolerant with regards to pH but often don't like fast changes.

Optimal pH is often related to other water quality parameters; ammonium & carbondioxide being the most obvious ones.

A particulair system often has the highest productivity at a particulair narrow pH range and a different filter design can shift this point while working with the same fish species.

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Hardly scientific but my murray cod at home go's of the food when pH drops below 5.8.

 

Yep, that's pretty consistent with most peoples reports for most species.... but I wonder if that's perhaps related to a rise in ammonia due to nitrirification shutting down

 

 

while they don't mind the 8.5 they face now and then if I overdose with base.

 

That's a serious "overdose"... :D

 

That kind of swing probably isn't good for the fish

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I sort of know the answer to this one however to chime into the thread possible knowledge for myself or someone else - when adding lime to adjust pH, how long after you've added it should you test it again?

What I noticed (which I have assumed is normal thus the question) - if I test the pH very soon (like 10-15mins) after adding the lime the pH has swung wildly and testing the following day the pH has risen only a little from its 'maximum' low reading.

Add a little more lime, test again straight away and it's high until the following day.

It took me a little while to get it back up to 6.2-6.8 but I always wondered if those swings in pH directly after adding the lime was a problem or not.

That was awhile ago now, I keep a much closer eye on it now but did find it interesting that it swung so much, immediately after adding the lime only for it to settle down again if only a little higher than the previous reading. When it did happen I just assumed that was normal

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Yep, that's pretty consistent with most peoples reports for most species.... but I wonder if that's perhaps related to a rise in ammonia due to nitrirification shutting down

 

 

That's a serious "overdose"... :D

 

That kind of swing probably isn't good for the fish

Ammonia isn't changing  much (to be more accurate TAN isn't changing) with pH as the system is virtually empty at this moment. Also pH drops gradually so filter has plenty of time to adapt. Low pH problems are probably more related to problems of the fish to keep blood acidity at the appropiate level.

 

On the high pH; I shoudn't have posted this earlier, its obvious poor practice to induce large pH swings. It occurred a couple of time, as the operator (me) had to adjust to much lower biomass and the lower buffering requirements. I was just surprised that the spiking pH didn't seems to bother the cod.

In a heavy loaded system pH swings will impact nitrification serverly as filterbacteria need time to adapt (more then the fish), this can results in nitrite/ammonium spikes.

 

Typical in commercial aquaculture RAS pH is tightly controlled with a alkaline dosing pump & pH controller.

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Hardly scientific but my murray cod at home go's of the food when pH drops below 5.8.

 

Why does your murray cod go off food when the pH drops below 5.8?

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Why does your murray cod go off food when the pH drops below 5.8?

Water quality not optimal for them (that simple), unhappy fish don't feed to satuation. First signs of unhappy fish is always reduced feed uptake and thats why feeding time (feeding response) is the best time to assess fish health.

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