kh from 5 to 0 in a week?! - Page 2 - The Planted Tank Forum
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post #16 of 18 (permalink) Old 06-21-2013, 01:46 AM
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Seems to me there's something inside the tank absorbing the KH.
I agree.
One of the biggest culprits is often high CEC substrates such as Safe-T-Sorb and related materials, and several of the ADA substrates.
I have not seen that with EC.

Organic processes can break down the carbonates. Some microorganisms use the carbon from carbonates. It takes a long time with no replacement (water changes) before the KH will start dropping from this, though. (You can do more research using the term Old Tank Syndrome) It sure does not happen in a week! More like several months to a year.

As noted above plants without added CO2 can start to use the carbon from carbonates. This also will not drop the KH from 5 degrees to 0 in a week.

Maybe try this:
Set up several glasses of water, and treat each one in a different way. Each one gets something from the tank, but only one thing.
One glass gets a handful of substrate.
One gets a bit of rock or driftwood (if you have either in the tank).
Another gets only what ever fertilizer you are using.
Another just gets some dechlor.
... and so on, until you have tested everything you are using in the tank.
Run each test for a week, and test the KH perhaps mid-week, then at the end.

Here is a way to make the KH test more sensitive:
Use only half test water, and half RO water. (test the RO to be sure it really has zero KH).
When you count drops to see what the KH is, count like this:
One and a half
Two and a half
... Each drop is half a degree of KH.
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post #17 of 18 (permalink) Old 06-21-2013, 02:02 AM
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Originally Posted by happi View Post
PH crash are myth when they occur with having 0kh or related to Co2. the ph crash doesn't kill fish, sudden change in KH will kill them. if you want to experiment it, try this: make sure you have 0kh water and with fish and co2 running, if you measure 5.0 PH in your tank, suddenly change the water with 0kh water, which might measure 6.2PH and you wont see dead fish, that is a big Ph swing by 1 point.
i use tap water on my 75g with UP aqua soil. my taps kh is 3 but this tank has kh 0. is that a dangerous change when i do a 50% WC? my fish seem fine...

so what is it that causes tanks to crash? i have never experienced this so i have only what i have read to go on.

8g Fluval 1M CT Betta
125g 5 Blood parrots, 1 Green Severum, 8 Dension Barbs, 10 Yoyo Loaches, 1 RTS
75g Angelfish, 3 EBGR, 4 Siames Alage Eaters, 12 Harlequin Rasboars, 1 BN Pleco, 1 Swordtail
33g long cherry shrimp, 8 pygmy corys, 5 ottos
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post #18 of 18 (permalink) Old 06-21-2013, 02:23 AM Thread Starter
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Diana, thank you! Looks like i have a bit of a long road here. Like i said it is a very aimple tank. Eco complete as substrate and plants. There are no rocks or driftwood at all. Thank you everybody for the input. Im gonna be busy
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