pH and tannins - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 14 Old 05-26-2011, 02:13 PM Thread Starter
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pH and tannins

Hey guys, I had a quick question. Right now I'm leeching tannins into my 26 gallon tank to help lower my tap water pH. On the first day it was at 7.4, but now its back up to 7.8. How long does it take for the tannins to lower the pH? Thanks!
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post #2 of 14 Old 05-26-2011, 02:23 PM
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Tannins will only lower ph if the buffering capacity is low.. If your Kh is high, it might take quite a while.

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post #3 of 14 Old 05-26-2011, 03:29 PM
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And maybe never. You can find out the hardness of your water from the supply people, many now have a website with water data posted. Find the GH (general hardness) and KH (carbonate hardness) if you can. When we know those numbers, we can offer suggestions.

Also, as your pH is rising, we might as well look at something else...is there any calcareous substance in the aquarium? Gravel, sand, rock made of calcareous rock (limestone, marble, dolomite) or coral (shells, coral sand...)?

Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #4 of 14 Old 05-26-2011, 03:59 PM Thread Starter
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Well, my water is really hard, with a 12 degree hardness and pretty high kH, can't recall it exactly but I know it's pretty hard. And my tap is at 7.8, so I found it interesting that it would lower and then go back to ita starting pH. The only thing I have is play sand, no rocks or any shells of the sort
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Just wondering cause I didn't want to mix ro water with my tap to lower it, but If I have to I'll do it.

Last edited by excal88; 05-26-2011 at 04:16 PM.
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post #5 of 14 Old 05-26-2011, 04:09 PM
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OK then, assuming you have very hard water with a high KH, it will buffer the pH to prevent it from lowering. The buffering capacity depends upon the degree of hardness, and the effect of tannins from a bit of wood is unlikely to have any effect until the point at which we exhaust the buffering capacity.

Neither would many pH adjustment preparations, and the danger in using any of those is the fluctuating pH (going down then back up again). If the buffering capacity is finally reached, the result could be a sudden and significant drop in pH, which can kill many fish outright. I'm not implying your intention to try these, just pointing out their dangers.

The safest method is to soften the water, and this can be done in a few ways. But we would need to know the hardness numbers in order to assess the best.

Byron.

Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #6 of 14 Old 05-26-2011, 05:39 PM Thread Starter
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Yea, here's the pdf file on my local water info. Its a bit old, based off of 2010, but its still better than nothing.

http://www.irwd.com/assets/files/bro...2010%20WQR.pdf

Apparently my tap has 45 ppm worth of nitrate. Crazy. kH is 10, gH is 12. Sorry for not being able to post up more specific details, not that good at reading the data.
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post #7 of 14 Old 05-26-2011, 07:57 PM
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Originally Posted by excal88 View Post
Yea, here's the pdf file on my local water info. Its a bit old, based off of 2010, but its still better than nothing.

http://www.irwd.com/assets/files/bro...2010%20WQR.pdf

Apparently my tap has 45 ppm worth of nitrate. Crazy. kH is 10, gH is 12. Sorry for not being able to post up more specific details, not that good at reading the data.
There is a lot of variability in that report, but I think we can accept that you have medium hard (or harder) water. So there is going to be stable buffering. Was there a reason you wanted to lower the pH?

Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #8 of 14 Old 05-26-2011, 08:09 PM Thread Starter
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Oh, I plan to have cory cats in the tank, and I read up that they prefer softer/ more acidic water. Realistically I want a more neutral pH, say 7.2-7.4 as it would be nice for my cory cats to spawn *if I have male/female pairs :P* but other than making it a bit more comfortable for my fish, theres not a big reason for lowering the pH.
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post #9 of 14 Old 05-26-2011, 08:14 PM
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Originally Posted by excal88 View Post
Oh, I plan to have cory cats in the tank, and I read up that they prefer softer/ more acidic water. Realistically I want a more neutral pH, say 7.2-7.4 as it would be nice for my cory cats to spawn *if I have male/female pairs :P* but other than making it a bit more comfortable for my fish, theres not a big reason for lowering the pH.
If you're working with tank-raised species, you will (should) not have a problem with long-term care and it should be possible to spawn them, other things being provided. But if you are dealing with wild-caught species, spawning would be very unlikely without very soft water.

It is actually the hardness more than the pH, though the pH tends to be relative to the hardness so it naturally falls if the hardness falls. Hard water affects soft water fish in various ways, and many will not spawn or if they do the eggs cannot be fertilized or do not develop properly due to the effects of the minerals in the water.

Having said that, if you want you can soften the water by diluting the tap water with RO (reverse osmosis) water, distilled water or rainwater (if it is clean, meaning no toxins). Depending upon the tank size, this can be a viable option. Once the initial water is soft or softer, the pH will naturally fall a bit, and the biological workings will keep it fairly stable. Water changes can be smaller and should not affect this too much.

Byron.

Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

Last edited by Byron; 05-26-2011 at 08:18 PM.
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post #10 of 14 Old 05-26-2011, 09:02 PM Thread Starter
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If you're working with tank-raised species, you will (should) not have a problem with long-term care and it should be possible to spawn them, other things being provided. But if you are dealing with wild-caught species, spawning would be very unlikely without very soft water.

It is actually the hardness more than the pH, though the pH tends to be relative to the hardness so it naturally falls if the hardness falls. Hard water affects soft water fish in various ways, and many will not spawn or if they do the eggs cannot be fertilized or do not develop properly due to the effects of the minerals in the water.

Having said that, if you want you can soften the water by diluting the tap water with RO (reverse osmosis) water, distilled water or rainwater (if it is clean, meaning no toxins). Depending upon the tank size, this can be a viable option. Once the initial water is soft or softer, the pH will naturally fall a bit, and the biological workings will keep it fairly stable. Water changes can be smaller and should not affect this too much.

Byron.
Ah, I see. I am not sure if the ones I got were wild-caught or captive bred, but the water should soften naturally, correct? It'll just take some time. I'm all for natural occurring things, so I want to avoid additives if possible. For now I guess I'll let the tank sit and simmer on its own. Thanks for the tips Byron.
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