Tannins & High TDS readings - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 08-02-2014, 04:10 PM Thread Starter
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Tannins & High TDS readings

I have a couple of tanks with Malaysian driftwood that still, about four months in tanks, is releasing tannins. One tank, 10g shrimp tank HOB filter, has a TDS of around 370. No chemicals or treatments of any type are added to this tank. All water is RO. The tank contains 10 Pumpkins, driftwood and Java Moss. 10% weekly water change with RO water. Shrimp are fed maybe once a week w/ barley. Long story short the only think I can come up with and am asking is can the high TDS reading come from the tannins alone?

The second tank, 26B w/ canister filter, does have a lot of livestock, is heavily planted and does get dosed daily with fertilizer so I would expect it to have a higher TDS reading and it does around 530. Again I'm wondering of the tannins are making the reading so high. I've even been giving this tank 20% water changes weekly with RO water.

Fish, shrimp, & plants are all doing well so I'm not as concerned as I am puzzled. Thank you for any input.

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Last edited by DayOlder; 08-02-2014 at 05:13 PM. Reason: Spelling
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post #2 of 9 (permalink) Old 08-02-2014, 05:53 PM
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Not sure if tannins can do that. The water I prepare with peat moss has low TDS, only a trace higher than tap, and I think that is other things I may add.
Ferts sure can raise the TDS though!
If you have a spare chunk of wood stick it in a bucket with some RO and test the TDS every few days.
Food can do this, too. Perhaps you should be doing larger water changes to get rid of the remaining things that the plants are not using.

Have you tested the RO? As the membranes age they let more 'stuff' through, and rising TDS is a signal to change the membrane.

If the RO is OK, then you can lower the TDS by doing more frequent and larger water changes. Not so large that it creates a big drop in any one water change, though.
If the shrimp are OK with a 10% water change, why not do that more often, and start lowering the TDS (If that is what the shrimp want). Similarly on the other tank. Doing the same 20%, but 2-3 times per week. This would start to get rid of the excess fertilizer that has been building up.
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post #3 of 9 (permalink) Old 08-02-2014, 07:01 PM Thread Starter
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I always check the RO before using it and yes it does vary depending on where I get it. The 6 gallons I used yesterday had a TDS of 20. I like your great idea of trying driftwood in RO. I'll try to set that up today. For shrimp I would prefer a reading about 250 but if I find out its just tannins raising the TDA I won't be concerned.

I tried increasing the number of water changes, using the same percentages, to every third day. But even then the TDS numbers, while being lower immediately after the change would be back to their original numbers by the third day.

I should add the filter media in the two tanks is completely different. The canister tank has balls, disks, pads and charcoal. The shrimp tank has only charcoal. Actually the only common thread between the two tanks is Tannins & RO water.

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post #4 of 9 (permalink) Old 08-02-2014, 08:13 PM
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That is odd. My old blackwater tank never showed high TDS readings, and that was after adding the water that I boiled the leaves in to make it darker. Never got over a TDS of 90.
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post #5 of 9 (permalink) Old 08-02-2014, 08:29 PM
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It has been said by many on here that charcoal only last a couple of weeks at best
before it looses it's ability to absorb due to already being saturated.
It is frequently kept as a med remover to be used after completing the "cure".
But generally I hear on this forum that most don't use it regularly in their filters.
If all of the other remidies you try don't have the effect you want, I'd try removing that charcoal. Not that I think it could be the sole cause, but rather a potential
contributor as it too is a common factor in both tanks.
I will not take any type of offense if anyone states that this is not correct as I am only interested in the benefit to the tank/shrimp so critique welcomed on this.

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post #6 of 9 (permalink) Old 08-02-2014, 08:42 PM Thread Starter
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Raymond,

Your right in that charcoal is another common denominator. Actually in my case it's Marineland Premium Carbon Ammonia neteutralizing blend but same thing. AnywayI already have Humic for the shrimp and Purigen for the fish on order to replace the charcoal. Media being so expensive I was trying to use up the charcoal I had left but believe now I'll just put it in storage and make the switch and see what happens.

Bump: The RO I got today had a TDS reading of 03. They must of just changed the filters. That's the lowest I've ever seen.
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post #7 of 9 (permalink) Old 08-02-2014, 08:55 PM Thread Starter
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Quote:
Originally Posted by ngrubich View Post
That is odd. My old blackwater tank never showed high TDS readings, and that was after adding the water that I boiled the leaves in to make it darker. Never got over a TDS of 90.
My tap water comes out at 120. I'm starting to wonder if my meter needs calibration.
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post #8 of 9 (permalink) Old 08-02-2014, 10:45 PM Thread Starter
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Took 8 oz of water, TDS= 20, added 1 Almond leaf. In 15 min TDS was 50. Will keep running to see how high it gets but it already seems to indicate that tannins increase the TDS or at least the reading of TDS.

1 hour TDS= 75

3 hours TDS=134

That completes my test, my wife needs her bowl back. Make your own conclusions if any. For me it tells me that at least for me my TDS reader is meaningless if there are tannins involved. Thanks to Diana for the suggestion.

Last edited by DayOlder; 08-03-2014 at 01:30 AM. Reason: Update
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post #9 of 9 (permalink) Old 08-02-2014, 11:53 PM
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ngrubich didn't mention which type of leaves he boiled, but still his statemen seems that it could indicate the high TDS are leaf type specific...or not if he also was using Almond leaves. At the time I once used leaves for tannins I got a PH that lowered as you added leaves. But then I was using Cypress leaves and they came from a pond
near me that is formed by damming up a stream which runs through a Cypress bottomland. The PH of the water in that pond is a wopping 6.4
Didn't have a TDS meter at that time but been trying to make it over there for a picture of a plant there for someone on the forum. Could bring my TDS meter/w me just for laughs. Stopped using the Cypress leaves when I found they would drop my PH that much if used excessively. 6.8-7.2 is fine/w me.

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