Magic numbers

[Underhill]

After keeping various types of fish for the past several years, I have heard a variety of parameters listed as being most important for fish. One of the most commonly used and tested number is pH. This is even more true for more sensitive fish like dwarf cichlids. However, I've also heard that pH is not truly that important for the fish's health. I've read that other than its effect on the toxicity of ammonia, pH is not really that important for keeping even the most sensitive of fish. Instead, the water's hardness is listed as being of great importance. These articles/posts have stated that the amount of dissolved salts like calcium, sodium, and magnesium are what fish sense and are, therefore, sensitive to. I think that it is an established fact that clean water of the correct temperature is the first essential component to keeping any fish. This of course, means that toxins such as, chlorine/chloramine, ammonia/nitrite, heavy metals, and CO2 and other dissolved organics must be kept low or negligible. But, what is more important the fish, pH or hardness? Are fish affected by water with the same pH but drastically different TDS? In my experiences, they seemed to be. Are they as sensitive to changes in pH without a change in TDS? I don't know. So which parameter is more important to keeping dwarf cichlids?
Jack

 

[tjudy]

Good topic Jack!

I think that the answer to the question depends upon what the aquarist is hoping to accomplish. If the goal is just to maintain the fish, the acceptable parameters are very broad. They only thing that one needs to watch is fast and drastic swings in either the pH or the TDS hardness. Of the two, however, I think that the pH is much easier to change fast and drasticly (short of dumping in a bunch of salt). Therefore, pH should be the first concern.

If the aquarist is trying to breed the fish, however, then TDS hardness and carbonate hardness (KH) are probably more important than pH. I did not have a lot of success with my Pel. taeniatus until I got the conductivity down to less than 50 mS, and the KH below 2. I was only able to accomplish this with the use of RO. My tap starts at 1300 mS and KH 8. An elevated KH probably affects hatching and development negatively. I would get spawns, but they would be small and never succeed. After changing the water, I had many successful spawns of many fry. When the KH is reduced there is a greater opportunity for the pH to go down. Luckily, fish that like low KH also seem to like a low pH... the two go together.

 

[Underhill]

pH, TDS

Ted,
Thanks for the response. You have mentioned kH in your water. I had been seeking to avoid the whole kH/GH thing. These are another group of parameters which cause (me, at least) a great deal of confusion. As I understand it, KH measures the amount of carbonate buffers in the water. These can be and often are, calcium but, the calcium can also be replaced with sodium, potassium, and others. I have also read that when peat is used it will affect the level of carbonate buffers because of the way it's humic acids bind the minerals in the water that register as hardness. While GH or general hardness is ... wait, what is GH? So, I had tried to use TDS (total dissolved solids) instead. I know that you, and others on this forum know a great deal about these substances but, I'll try to spell the terminology out so that those who are newer, as we all once were, will be able to understand.

You mentioned the relative ease with which one can manipulate pH especially with reverse osmosis (RO) water. However, the question stll remains, why do the fish need lower pH. Is there a physiological need for certain fish to be in conditions where the acidity of the water is high? I can see how fish from very soft and acidic waters like many dwarf cichlids would require soft and acidic water to simulate the tannin rich, rain-swollen rivers, streams, and flooded areas that they inhabit. This would especially be true during the rainy season. These soft and acidic conditions would serve as a signal to the fish that the rainy season is at hand and that the forests and grasslands have been flooded, providing the necessary food and habitat for breeding. I can see the physiological reason for these conditions as a programmed trigger again, for breeding.

Notice I have said soft and acidic above. What I don't understand is the value of acidic water that is not necessarily soft. As you have said the problem can be circumvented altogether through the use of RO water. But, I'm trying to determine the value of merely acidic (low pH) water for these fish. I too have used RO water at various pHs with success in breeding these fish. I'm trying to determine when keeping these fish if it is important to adjust the pH of one's water to meet their needs. Obviously, this is much easier to do and cheaper on a small scale, than softening water with deionizers or RO units. But, is it really worth it? Is there value to acidic water that is fairly high in TDS for soft water, dwarf cichlids. I can and do, easily lower my pH quite a bit in planted aquaria with CO2 injected (pH, 6.7). But, does this provide any benefit to say, a trio of wild-caught rams (other than having pretty hiding places) over my tap water with a pH close to 7.3? If so, what is this advantage and how does it impact the fish? Thanks again, and I hope this has been coherent enough to merit a response. I look forward to any insight.
Jack

 

[tjudy]

I think that you might be looking at this from the wrong direction. Your questions sounds like 'Why would a fish choose acidity?"... The environemental conditions are what drives the evolutionary change in a population. The acidity came first, and the fish that could handle it have survived. Species that have evolved in hard, alkaline conditions would not be able handle acidity well at all... and vice versa.

What is the specific physiological difference between soft and hard water fish? I do not know for certain, but I would suspect that sensitivity to electrical conductivity might be an issue. Soft water fish that live in water that is not very conductive, might have a problem with stray voltage that can come from power heads, heaters and other electric things. I could just as easily be TOTALLY off base on that though.

Your description of KH is correct. GH (general hardness) is the same as TDS or cunductivity (mS). All three measure the same thing. TH (total hardness) is a measure that is used in Europe sometimes that is a combination of GH and KH. I do not use TH, so I am not entirely familiar with it.

As to your question about whether we really need to worry about pH and hardness in concerned, I think that many of us over emphasize it. Natural ecosystems see huge shifts in water chemistry during rain events and droughts. Sediments in runoff are going to add hardness, while decomposing organic matter (like in floods) will decrease pH. These shifts can occur over very short periods of time. Swings can occur in less than 24 hours. I have done farm pond measurements and seen the pH swing by two points in a day simply due to daytime photosynthesis pulling CO2 out of the water.

 

[Underhill]

Importance of pH

Ted,
Again, thanks for the reply. Your response is very informative. However, I may have been somewhat confusing in my questions and led us slightly off topic as a result. I can see the significance of TDS for fish of all types. Whether it affects them because of electrical conductivity or more fundamentally at the cellular level and below because of osmotic properties of water with different TDS ranges. What is not clear to me is the importance of certain pH parameters for fish. In other words, why is it beneficial for a fish from a soft water biotope to have water with a lower pH say, in the 5.7-6.3 range versus the same fish in water that has a higher pH, 7.4 if, both situations have water with the same level of TDS. Again, this question stems from the idea that to keep soft water fish you must lower the pH. This can come at the cost of actually raising the TDS with many of the available commercial products. If I add a pH minus product that adds buffers to the water, does this benefit my soft water fish? I have heard both answers to this question and this has led to my confusion.
If I had to guess (always a dangerous thing for me :wink: ) I'd say that pH is probably not irrelevent for fish keeping. But, the focus for keeping soft water fish like apistos and most dwarf cichlids, should be on the hardness of the water. I think that soft water at a range of pH's is what is needed for proper keeping, within reason, of course. I'm just not sure how far this can be taken. In other words, if someone had very soft water, could their water have a pH higher than 7.0? If so, would this affect the fish? :? O.K., I'm making my head hurt, time for another cup of coffee!
Jack

 

[Zapisto]

just one thing guys.

excellent topic.
i read it with a lot interest , and i think i am agree with ted theory.
but as he say , everything depend on what the goal of the keeper.
nice

 

[tjudy]

I keep going back to the concept that in the natural environments there is a correlation between soft (TDS), low alkalinity (KH) and acidity. They go together. To keep a fish in low pH and low KH,but high TDS, is only providing the fish with two thirds of their requirements. 2/3 is better than 1/3! If the parameter that is off is not off by much, then there is probably not goign to be any problems.

I heartily agree with your assessment that the pH reduction chemicals increase TDS. The product I like is Seachem's Acid Buffer. The conductivity reading jumps, but goes back down. Since I began using RO, I found that I needed very little to drop the pH to 6.0 from 7.0. I also found that a KH of 0-1 results in the pH decreasing in a tank naturally. If you do not want to use a product, but are using RO, try putting peat in the tank filter. That should reduce the pH pretty quickly if there is little to no KH.

I am moving to an area that has tap water with extremely low KH, a pH of 6.7 and a conductivity of only 160 mS. I am excited about this! I have never lived anywhere with water that good! I have 100 gpd RO/DI, but I probably do not need the DI anymore. I am going to play around with using the stage cartridge for the DI to hold a packed peat block. That stage comes after the RO. I imagine that I will be able to get water out of the unit with 0 KH, <10 mS and a pH of about 5. If I mix that 75% filtered to 25% tap, I SHOULF get a KH 0-1, 25-40 mS, and pH around 6.0. PERFECTION (IMO).

The cost is that I will live NOWHERE near any LFS, over two hours from a commercial airport, and in an area where UPS, FedEx and every other delivery service has their highest 'rural' rates.

So if I buy fish from any of you PLEASE cut me a break so I can afford to get them to me!

 

[Neil]

Jack,
I think that you need to look at this from a perspective of what is best, and not necessarily perfect. The pH of the water is not as critical as the hardness. But, as Ted says, it is difficult to completely seperate the 2. So, if you think of it in terms of what will give your fish the best water, you should be attending to the hardness.
pH is like temp. Apistogramma can handle a fairly wide temp. range, but are much happier in a narrower range. Also. they are more likely to start breeding and have a more even gender ratio of fry in that narrower range. What specifically does acidic water do for soft water species? Could be alot. Might be not much. More likely it is important to their osmoregulatory system, their immune system, their reproductive system and much more. If we live in an area where air pollution is higher than average (but not terrible), does it affect us? Well, it will affects some of us more than others, probably across a wide spectrum. That is because there are other things probably at play - diet, stress, general health (both genetic and environmental), etc.
Hardness is more significant to the fishes well being because it is more akin to the air that they breath. Softer water is like cleaner air. Doesn't mean that they will have specific problems in a little harder water, just that they will be generally healthier. Acidity is more akin to the humidity of the air. How comfortable they are in their water will determine much they feel like searching for food, defending territories, breeding, etc.
This is probably an inappropriate comparison, but the only one I could quickly come up with. Suffice it to say that what Ted mentions:

The environemental conditions are what drives the evolutionary change in a population.

means that these fish likely not only have developed a way to handle it, but also now have (at least in an evolutionary short-term sense) developed a reliance on it.
If water is too hard, many apistogramma species' eggs will not develop properly. If the water is too alkaline, they may not want to breed in the first place. This is all I need to know for me to make an effort to replicate the conditions of the habitate where they came from, because breeding is my primary goal.
Neil

 

[Underhill]

Thanks

I apologize for taking so long to respond to the wonderful replies I received on this topic from both Ted Judy and Neil. This has brought some clarity to an area that has long been troubling me in the hobby. I will conclude this by expressing my gratitude for your insight and post a link to a similar discussion on this topic I had with the members of "The All Wet Thumb Community" forum for planted aquaria by "Aquabotanic." I hope that others have learned from my ignorance and the wisdom of those at both these forums. Thanks again and keep up the great work!

more discussion here...
http://aquabotanicwetthumb.infopop.cc/6/ubb.x?a=tpc&s=4006090712&f=6806023812&m=1336023563
and continued here...
http://aquabotanicwetthumb.infopop.cc/6/ubb.x?q=Y&s=4006090712&a=tpc&m=1776053663&f=6606090712

Jack