PH too Low, can't maintain KH - where is the acid coming from? - The Planted Tank Forum
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post #1 of 19 (permalink) Old 01-24-2006, 06:35 PM Thread Starter
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PH too Low, can't maintain KH - where is the acid coming from?

My tank is down to 5.0pH WITHOUT CO2
I can't keep the KH up. It is at 0
my GH is 6-7
TDS was up to 1300ppm before last nights WC


Tap is:
7 pH
0 dKH
3 dGH
150 TDS

I have been doing 40-50% w/c every 7-10 days and adding baking soda to bring the the pH and KH to the point I can turn on the CO2 and it just keeps coming back down again- pH from 6.4 to 5 in 3 days. The more baking soda I add the higher my tds gets, but the KH and pH keeps comming back down right away.

Could my drift wood be leaching some sort of acid into the water? It the only thing I can think of. Substrate is aquarium gravel and ecco complete. Nothing else in the tank except plants and fish.

Any tips on how to get this to level out at a reasonable place? Something other than baking soda maybe?
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post #2 of 19 (permalink) Old 01-24-2006, 06:37 PM
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Some people used crush coral in their filter.

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post #3 of 19 (permalink) Old 01-24-2006, 07:20 PM
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Quote:
Originally Posted by turbosaurus
Could my drift wood be leaching some sort of acid into the water?
It definitely could be. I have experienced 'toxic' (my term) driftwood before. In my case, it would eat all of my GH and KH over the course of a couple of weeks. I'd test some of your driftwood by putting it in a plastic container with tap water and just monitoring the readings over a week or so.

In my case, since the wood wasn't leaching any tannins, I was told by a respected aquatic plants member that the driftwood much be leaching strong acids (e.g. via internal decomposition or some such) and that I really couldn't cure it. So, I ended up tossing the driftwood.

Good luck!
Brian.
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post #4 of 19 (permalink) Old 01-24-2006, 07:34 PM Thread Starter
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UUUGGGG,
I was hoping that wouldn't be the answer...
Its a 180 gallon tank. I spent 18 hours over 4 days taking it apart down to gravel specifically to putting in the new wood- which I had to screw to slate, that I had to drill holes through and replanting the whole thing specifically to get this monster piece of drift wood in there! I don't want to take it out!

I Think I read that limestone will raise pH- I have pieces of limestone tile left over from my bathroom floor project, I wonder if I replace the angels breeding slates with limestone would that help?
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post #5 of 19 (permalink) Old 01-24-2006, 07:38 PM
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Hmmm. I wonder if your carbonate is precipitating out for some reason....

You might look at seachem.. they offer several buffers which can help maintain a ph range... but that could get expensive.

But the weird thing is the dropping to acidic conditions... that exactly backwards of anything I"ve ever experienced.

General hardness can be brought up also by adding Epsom Salts as well as baking soda. Then you'll get magnesium in addition to the sodium from the baking soda you're adding... but that won't help your Kh problem... which is impacting your ph.

This review is more for myself...

Gh is actually a measure of the calcuim and magnesium, the dissolved minerals in your water. Gh doesn't actually do much to change ph. Gh is more important for deciding what "hard water"/high Gh or "soft water"/low gh plants or fish to add to your tank.
while
Kh is a measure of the ratio of bicarbonate and carbonate ions in the water. So, Kh is actually a measure of the buffering capacity of your water (oversimplifying it is a measure of the ability of the water to maintain a stable ph). Kh has a lot to do with maintaining a stable ph and being able to change the ph easily or not.


Your water chemistry may be causing a shift in the bicarbonate/carbonate balance. The ratio is getting whacked out... and thus your water can't 'buffer'...
Seems like something is acting as an acid source in your tank... You might try taking all decorations including driftwood and the like out of your tank.

Did you clean something with acid like hydrochloric or muritic acid, sometimes it's used for cleaning swimming pools or plumbing and equipment?

I think you should try adding both calcium carbonate as well as sodium bicarbonate... since too much sodium is bad for your plants as well... and calcium will help your gh as well as your kh...

You can buy it, you might try a pharamacy.. but pharmaceutical grade chemicals are expensive... or look for common sources of it like some antiacids, agricultural lime for use in making cement, look for 100% calcium carbonate or better yet...
you might try a fish store that specializes in marine tanks... look for kalkwasser supplement... (means chalk water). That will help raise your KH and GH.

hmm... just a though...
these minerals are 100% calcium carbonate... calcite, aragonite...
but adding crushed rocks to your tank won't be controllable or measureable and will be a very slow method of getting the calcium and carbonate levels raised up.
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post #6 of 19 (permalink) Old 01-24-2006, 07:41 PM
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one more thought... for good pricing on stuff

http://www.gregwatson.com/DryAquaticFertilizers.asp

has calcium carbonate for sale...

He's got a lot of useful dry ferts and chemicals
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post #7 of 19 (permalink) Old 01-24-2006, 07:43 PM Thread Starter
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No- I never use any cleaning solutions in/near the tanks- just dechlorinated water and elbow grease.
Thank you for the tips on where to find Calcium Carbonate without getting banged over the head.
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post #8 of 19 (permalink) Old 01-24-2006, 08:34 PM
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If you anything else to the tank you're going to be raising the TDS even more. You really need to find the source of the acid. I'm assuming that your fish load isn't ridiculous and that you don't have a huge mass of rotting plants somewhere. Beyond that, its probably the driftwood.

I really don't think you have an option. It has to go.

If you really felt the need to get the pH up I'd go with pure KOH (potassium hydroxide). It is a quite potent base. A very small amount would offset a large quantity of acid. You might find your KH restoring itself to some degree too, which would be an overall benefit. I would advise against any more NaHCO3 since you'll get a very large sodium load. This will certainly hurt your plants and fish, even if the acidic pH doesn't.
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post #9 of 19 (permalink) Old 01-24-2006, 08:59 PM
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I had the same problem as you, my PH was down in the 5.0 range, i bought crushed coral and put it on top of my gravel as well as in my filter, and now my ph stands at 7.1.

I was recommended this by a very knowledgable LFS employee. Its cheap and natural and thats what was important to me. I dont like using chemicals.

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post #10 of 19 (permalink) Old 01-24-2006, 09:58 PM
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Crushed coral is used by folks, such as myself who have very soft water. I use 1/3 of a cup on my 90 gallon with pressurized CO2. It gets my KH to around 7 and seems to last for about 3 months, before disappearing completely.

I did however read somewhere, and I am not sure of the truth of this, that it is possible to set up a bad cycle with Crushed Coral and very low pH. I'm sorry I don't have an explanation or more info on this, but you may want to do some research as to what happens to crushed coral in exremly acidic conditions.

If the wood is the culprit, and you keep adding crushed coral to offset the pH, you are chasing the dragon, and the tank will most likely never be completely stable.

Hope this helps.
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post #11 of 19 (permalink) Old 01-24-2006, 09:59 PM
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Can the driftwood be treated to make it inert? For example, a penetrating wood epoxy?
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post #12 of 19 (permalink) Old 01-24-2006, 10:06 PM
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does crushed coral stop working after a while? I was under the impression that it lasts for a long long time.

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post #13 of 19 (permalink) Old 01-24-2006, 10:24 PM
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What did you put in to get your GH to go from 3 from the tap to 7 in the tank?

If you have large amounts of gunk rotting somewhere (in your substrate, under your drift wood, in your filter, etc) or lots of fish, you will be creating lots of nitric acid that will drop your pH and KH.

My tank has a similar GH, but the pH would be higher than 8 (closer to 9) if I used it straight from the tap (it's well water). I keep Discus, so take it down to closer to 7 with muriatic acid before I use it. In this range, the pH drops about 0.2 - 0.3 pH units per day because of the nitric acid build up from the breakdown of the fish ammonia and feces. Discus eat lots of stuff! This is a 55 gallon tank, so it should be slower in a larger tank. Because it's discus, I change the water every 2-4 days, to keep the nitrates at 10 ppm or below, so I don't worry much about the pH drop. I just add about 1/4 tsp of baking soda a day, to keep the pH at the same place each day. I also don't worry about sodium or tds because I change 60% of the water every 2-4 days.

The crushed coral idea should work for you, if everything else is OK. The complication of adding coral to pH 5 is that you will get a bunch of C02 liberated in the process. Could be a problem for your fish. If you do start adding it, do it a bit at a time. Or better yet, do a bunch of water changes to get your pH to at least 6.5 or so before you add the coral.
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post #14 of 19 (permalink) Old 01-25-2006, 01:54 AM
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Quote:
Originally Posted by Glostik
does crushed coral stop working after a while? I was under the impression that it lasts for a long long time.
Crushed coral IS CaCO3 (mostly). It stops working when it's gone. In a very large, bulky form (not powdered), it has a low surface area compared to CaCO3 powder. It dissolves more quickly when pH is low (injecting CO2 speeds this along), and more slowly when pH is high. I wouldn't think adding it to the filter would greatly affect immediate CO2 levels (or pH), since the rate of reaction is much, much, much slower than the rate of CO2 loss from outgassing.
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post #15 of 19 (permalink) Old 01-25-2006, 03:08 AM
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I agree that crushed coral would be a good starting point. Its what I use for very soft water. Maybe 2/3 to a full cup pea sized CC should really help bring up the pH and KH/GH. But you may have to add alot more. Definately don't want to go any of the pH up buffer routes, IMO. I'm a newbie, but I have had to deal with 5.2 pH out of my well water so I have a little experience. But my water raises to 6.4 or so pH after CO2 outgasses in 24 hours. I would want to know if it is the wood, if I were you. Could you cut off a small piece that you could screw back in later as a baseline test? Good luck.





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