# Effects of pH on breeding



## Chris S (Dec 19, 2007)

So I have sort of a question, but moreso I want to spark some conversation.

First off, I have to say despite my successes/failures in breeding, I still do not fully understand the direct effect pH has on breeding.

By breeding I mean anything from triggering spawning behaviour, fertilization of eggs and early fry/wiggler rearing. In fact, anything regarding the general process.

There are some generalities that can be made, and I want to try and steer the conversation away from them. One being that a low pH _typically_ means a low kH and, for the most part, soft water (so low conductivity, GH, TDS - however you want to measure it.) I know the effect that soft/hard water has on certain fish, as I'm sure many others do as well. That said, you can achieve soft water without it being acidic, or hard water without it having it be a high pH.

So how about it, how does pH effect breeding/breeding behaviour?


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## AquariAM (Jan 28, 2010)

I don't know, but I will tell you this piece of info I discovered by experimenting- Angelfish will spawn just as ridicufrequently in pH 7 kH 3 as they will in pH 7 kH 8- which is a pretty big difference. Using a buffer that increased kH but didn't effect pH I wanted to see what the effect would be- and apparently it wasn't much. I was keeping them in fully remineralized R/O


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## BillD (Jun 5, 2006)

My angels bred constantly at pH of 8 or a little more. Hatch rates were very good also. When Gary Elston spoke to us on apistos, he felt that soft water was more important than pH for those apistos that come from very soft acidic waters. I haven't tested for pH in years. Years ago i had occasion to speak with Joe Gargas, who was head of R&D for Wardley, as well as a regular contributor to FAMA, and his feeling was that pH was of little or no consequence, while TDS was important. One exception would be if you were adding alkaline water to acidic water with ammonium. The ammonium would convert to ammonia and you would have fish deaths. Those types of deaths would be attributed to "pH shock" which in fact it wasn't.


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## Cory (May 2, 2008)

In many cases the effect PH has on breeding is as a trigger for spawning. In certain areas the PH will shift predictably at the beginning/during rainy season and rainy season being the period with the most abundant food supply is the best time for fish to spawn. Reproducing the PH shift can trigger the urge to spawn in those fish which naturally spawn when that shift occurs. 

In other areas, PH can affect the hatch out rate of eggs. Eggs laid in very hard, basic water and very soft, acidic water have different mechanisms in place to deal with the type of water they are in. Sometimes that means a certain species' eggs will only hatch in a certain type of water. I think this probably has to do with how long a species has been endemic to an area and therefore how long it has had to specialize itself and tailor itself to that area. 

I can't think of much else right now as far as breeding goes but I pretty much never play around with PH or anything like that because I've never needed to yet, all of my fish breed fine in Toronto tap.


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## Chris S (Dec 19, 2007)

BillD said:


> When Gary Elston spoke to us on apistos, he felt that soft water was more important than pH for those apistos that come from very soft acidic waters.


This is sort of the conclusion I have come to.

I've been trying to use pH as more of a triggering effect, as Cory mentions.

So is it safe to assume that:

a) pH has no effect on egg permeability
b) pH has no effect on the fertilization process (sort of the same as a, referring more to sperm)
c) pH has no effect on development rates of fertilized eggs
d) pH has no effect survivability of fry (wiggler to small fry)

and that:

a) pH may have a triggering effect in some fish to induce spawning
b) pH may have a role in determining the sex of the fish

Might I also ask, what is the effect that pH itself actually has on fish (and I don't mean sudden changes in pH!) - does it effect metabolism, respiration, digestion? Anyone know of any studies, or documentation?


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## bae (May 11, 2007)

One effect pH does have is sex ratios of fry in some species. Some years ago there was some work done in which sex ratio for a number of apisto species at different combinations of temperature and pH was determined. IIRC, there is a critical period of about a week in which sex is determined, and if pH or temperature are too far away from the optimum during that period, you can get a skewed ratio. Outside this period it doesn't matter.

Many people have observed that pH affects sex ratios in kribs. Some other cichlids have genetic sex determination, or sex is determined by social factors, or the mechanism isn't known. I wouldn't be surprised to find that pH is a factor in sex determination in some non-cichlids.


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## Chris S (Dec 19, 2007)

I've read the same. Romer did a big study on it. From my experience, and many others (including Romer as well), it would seem temperature is more of a determining factor on sex with pH being secondary.

That said, it would be interesting to know why this is and what actually takes place in the development.


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## ameekplec. (May 1, 2008)

My guess from an evolutionary perspective would be that because pH is tied to environmental factors, varying the ratio of sexes according to whatever is more favorable (ie if low pH is favorable for plentiful food, then make more females to make more offspring to feed) would lead to better success of next generations.

Chris, to go back to your assumptions, I don't think a) and b) would hold true. Depending on the environment, the viability of gametes would be differently affected - too acidic and sperm can be rendered immotile. pH also apparently has effects on egg development once fertilization occurs, so there's a good chance that at any stage pH will affect the development of fry. Not sure what effects they might have on fry sex ratios, but certainly viability of ova is affected (although my knowledge of develelopmental bio is fairly limited).

Cory, I'd expect that those changes to water parameters tied to seasonal rains are more to do with temperature and conductivity of the water than the acidity, although I'm sure acidity plays a part in the development process nonetheless.


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## Cory (May 2, 2008)

My guess would be that at deeper depths where the temperature change is felt less acutely the shift in PH would be more likely to inspire spawning. Obviously in the amazon where the water is already soft and acidic rain water might not affect the PH too much but in other areas with more basic water rainy season probably dramatically alters the water chemistry. Since some fish like cardinal tetras wont spawn unless the PH is right it is reasonable to assume I think that it plays some role in triggering the spawning as well. Whether that be shifts in PH or just finding water with the right chemistry would depend on the fish I guess.


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## ameekplec. (May 1, 2008)

I wonder if it's the pH alone, or if it's just that when you change the hardness, it in general (in aquaria) results in a change in pH, so that it seems like a correlation where in fact it's not terribly important.

In terms of temperature differences, how deep does the water have to be before you get a thermocline in a river or fw body of water? I'd guess pretty deep unless it's a relative still body of water.

So, Cory, you need to have some tanks going now! You need a pH curve, and a temp curve. So, 10 - 15 tanks should be good.


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## bae (May 11, 2007)

Chris S said:


> I've read the same. Romer did a big study on it. From my experience, and many others (including Romer as well), it would seem temperature is more of a determining factor on sex with pH being secondary.
> 
> That said, it would be interesting to know why this is and what actually takes place in the development.


I've got a copy or a link to the Romer paper somewhere... I'll have to dig it out.

I don't know whether anyone has worked out how environmental sex determination works in any fish, but in leopard geckos, where sex is set by incubation temperature during a short critical period, one of the enzymes in the mechanism that produces the steroid sex hormones has a critical temperature range that affects its activity. This aromatase enzyme converts an estrogenic hormone to testosterone. At higher temps, where it is more active, there's more testosterone and less estrogenic precursor, and vice-versa at lower temps. Sexual development is triggered in one direction or the other by the balance during a particular short period in embryonic development. Since all vertebrates use the same sex hormones, there's probably similar mechanisms in fish that have temperature-dependent sex determination.

Reptiles have cleidoic (more or less sealed) eggs, while fish don't. It would be interesting to know whether the pH inside a fish egg or embryo is affected by the pH of the surrounding water. If it is, there may be something similar going on, since enzyme activity rates vary with pH as well as temperature.

It would be interesting to know how this works out in nature, where the sex ratio tends to be 1:1, or does it? Are parents 'motivated' to lay their eggs in places of specific temperature range or pH, or does it just all average out over many clutches in the end? Maybe skewed sex ratios are an artifact of the limited and controlled conditions in captivity.


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## Cory (May 2, 2008)

Well, I know that as far as temperature goes there have been studies done to determine how much the temp varies at different depths. Someone linked some of them on MFK a long time ago. I forget how many feet it was before there was a difference. In large bodies of water like lake victoria or something which can get incredibly deep in places I imagine there are various strata of temperature zones influenced by internal currents and other seasonal variations.


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## Chris S (Dec 19, 2007)

bae said:


> I've got a copy or a link to the Romer paper somewhere... I'll have to dig it out.


Cichlid Atlas I goes into the issue in quite some depth - I believe the rest of the book was built around his study of pH/temp on apisto reproduction!



bae said:


> It would be interesting to know how this works out in nature, where the sex ratio tends to be 1:1, or does it? Are parents 'motivated' to lay their eggs in places of specific temperature range or pH, or does it just all average out over many clutches in the end? Maybe skewed sex ratios are an artifact of the limited and controlled conditions in captivity.


Again, pulling from my limited knowledge based almost solely on apistogramma: I believe there is typically a higher % of males in the wild, as they are constantly the target of predators. Because they are more colourful and it is necessary for them to openly fight for their territory they spend much less time hiding amongst the leaf litter that is so common in their habitats. I believe Romer also wrote about this (but don't quote me!), also noting that dominant male apistos were often preyed upon more heavily.



ameekplec said:


> Chris, to go back to your assumptions, I don't think a) and b) would hold true. Depending on the environment, the viability of gametes would be differently affected - too acidic and sperm can be rendered immotile. pH also apparently has effects on egg development once fertilization occurs, so there's a good chance that at any stage pH will affect the development of fry. Not sure what effects they might have on fry sex ratios, but certainly viability of ova is affected (although my knowledge of develelopmental bio is fairly limited).


I would find it hard to believe that a-d would hold true if properly researched (or has it been?!).


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## ameekplec. (May 1, 2008)

Chris S said:


> I would find it hard to believe that a-d would hold true if properly researched (or has it been?!).


Likely it has as the zebra danio is a frequently used developmental model, so conditions around it have probably been researched to death - when I have more time I'll look up the literature on that.


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## Chris S (Dec 19, 2007)

Interestingly, I just recently read that pH has a very direct effect on fish sperm - ie. high pH can literally kill the sperm before it reaches the egg. I assume the reverse is true as well. I guess that makes perfect sense though, as pH has a large impact on human sperm as well.


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## BillD (Jun 5, 2006)

Perhaps hormones in the water will affect sex ratio. I was watching a program on frogs a few weeks ago, and African clawed frogs that have become established in California, have incidences of sex change. That is, a frog born as a male becomes a female and lays viable eggs. They had one such frog on the program. The theory is that the amount of estrogen in the water from humans using birth control pills may be the culprit. They have also found frogs in other areas that are almost hermaphrodites, that lend credence to this theory.


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## bae (May 11, 2007)

Chris S said:


> Interestingly, I just recently read that pH has a very direct effect on fish sperm - ie. high pH can literally kill the sperm before it reaches the egg. I assume the reverse is true as well. I guess that makes perfect sense though, as pH has a large impact on human sperm as well.


It must vary with the species, since fish are found across such a wide range of pH, 3-11, IIRC. I wouldn't expect fish from either end of the range to flourish at the other, but it seems like many can adapt to _some_ change toward 7 from either direction.

As for viability of embryos and fry, low pH inhibits growth of bacteria and fungi, so eggs of fish that normally spawn in very acid waters may not have adequate mechanisms to fight off microorganisms in more neutral water compared to species that normally spawn at higher pH.


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