pH situation + Crushed Coral - The Planted Tank Forum
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post #1 of 15 (permalink) Old 07-11-2016, 12:47 PM Thread Starter
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pH situation + Crushed Coral

Hello,

I have an interesting pH situation that I am looking for some advice on, or at least to pull some information from other's experiences.

I was having an issue with my pH, it was down in the low 6's, around 6.2.

I added 1 cup of crushed coral, split into two of my filters (1/2 cup in each). The pH shot up to 8.2 within a day.

My pH now remains constant at 8.2, great! However I was hoping to aim for around 7/7.5.

I removed 1/2 cup, leaving me with 1/2 cup, pH remained the same.

I then halved it again, leaving myself with 1/4 cup of crushed coral total. the pH still remains the same.

KH remains around 4 drops which roughly equals 40 ppm. (rather low still if you ask me).

I find it interesting how such a small amount of crushed coral seems to be affecting my water when all over the net it appears that most people use like 1 pound or even more and sometimes never notice an effect. I saw effects within the first night and it appears to remain at 8.2 even with 1/4 cup of it.

This isn't per say a problem, but I feel that 8.2 is a bit high for my personal preference and I am keeping Red Tail (or Blackline) Rasboras which tend to prefer a bit acidic water.
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post #2 of 15 (permalink) Old 07-11-2016, 01:46 PM
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Sounds like it's time for a water change.
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post #3 of 15 (permalink) Old 07-11-2016, 02:02 PM
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I agree with OVT. It is time for a water change.

I also use crushed coral in my tank as my pH is anywhere from 5-6 depending on the weather as I have well water.

To get to a pH of around 6.8, I added small amounts over 24 hour periods. My 29 requires 4 tablespoons while my 5.5 has less than tablespoon total. My 10 gallon is somewhere in between.

I had fish in two of the tanks when I did this, so massive pH swings wouldn't have worked. I played around the with amount needed for the 5.5 gallon before doing a fishless cycle on it.
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post #4 of 15 (permalink) Old 07-11-2016, 03:04 PM Thread Starter
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I do weekly water changes. pH stays at 8.2, doesn't go any higher.

Maybe 1/4 cup is too much? However I was surprised when a lot of the stuff I read on the internet indicated people were using like 1 pound and not noticing anything.. odd.

I was hoping to have some KH while retaining around 7.5 pH.

I may take more crushed coral out and start with just tablespoons vs cup

Last edited by Netcode; 07-11-2016 at 03:20 PM. Reason: added info
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post #5 of 15 (permalink) Old 07-11-2016, 04:29 PM
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Crushed coral is a form of calcium carbonate, which isn't very soluble in neutral pH water, but with low pH water it dissolves much faster. It looks like your water, with the coral in it, will stabilize at pH 8.2. If you use baking soda, sodium bicarbonate, you can adjust the KH to whatever you want, and get a stable pH. Crushed coral is much more useful for raising the general hardness, GH, instead of the KH.
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post #6 of 15 (permalink) Old 07-11-2016, 05:07 PM
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Quote:
Originally Posted by Netcode View Post
I do weekly water changes. pH stays at 8.2, doesn't go any higher.

Maybe 1/4 cup is too much? However I was surprised when a lot of the stuff I read on the internet indicated people were using like 1 pound and not noticing anything.. odd.

I was hoping to have some KH while retaining around 7.5 pH.

I may take more crushed coral out and start with just tablespoons vs cup
Start with small amounts and add them slowly. It will take a couple of days to get the pH were you want it and then all you'll have to do is test once a week to make sure the crush coral is doing it's job.

Adding too much at once stresses the fish out and sends you tank out into the land of instability.

I know it was suggested to baking soda, however, I've done that and it's a PITA. Crushed coral keeps things stable, longer and doesn't cause swings like baking soda.

Do I get points for not getting into a rant about how when everything is bigger, dosed more, ect... that magically makes everything 'better' in this hobby? Oiy! LOL
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post #7 of 15 (permalink) Old 07-11-2016, 06:08 PM Thread Starter
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I can't say I am a fan of Sodium Bicarbonate due to the fact that you always have to add it. Then it gets used up fairly quickly, and pH starts to drop. I like the idea of being more stable. Eventually yes the crushed coral is going to disintegrate, but that seems to take a while.

I wish my tap water naturally had a higher KH, as this was my main goal of using crushed coral, to stabilize the water more.

I will take more out and see if the pH does come down. In a 60 gallon tank I figured 1/4 cup of crushed coral wasn't going to do anything.
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post #8 of 15 (permalink) Old 07-11-2016, 06:30 PM
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I started using crushed coral a couple months ago. I do 50% water changes weekly ( more on the 5.5) and I have yet to replace the crushed coral that I added. The 5.5 gallon has been set up now for 8 weeks.

Your point about baking soda is exactly why I don't use it. It has to be added to the water for every water change or the pH plummets.

If you read any of the African cichlid forums, they love baking soda. I swear some of them have stock in the stuff. If they like constantly dumping stuff into their tanks and playing with water chemistry, that's fine. It's silly, but I'd rather add something once every couple of months instead of once a week or more.
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post #9 of 15 (permalink) Old 07-12-2016, 02:42 AM
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A lot of people, myself included, would kill for a stable pH of 6.2. My water comes out of the faucet at 8.2 to 8.4 and I spent a lot of time trying to keep it around 7. I lost that war.

My knee jerking reaction to threads like this is "don't fight your water". It is what it is - use what you got to your advanage. I strongly belive that stability is way more important then some specific number.

When it comes to well water my tune changes a bit (we just moved into a more rural area and we specifically avoided houses on wells only. But then I bitched to no end about our municipal water in every house that we lived in).

My personal issue with coral, peat, and such is that it's hard to keep stable.

Bump: usin RO and building your own design water might be a sustainable solutions for some.
Otherwise, look up GH Booster. Most of us dose the tank's daily for plants, so, what's the big deal of doing the same for the water?

Last edited by OVT; 07-12-2016 at 03:35 AM. Reason: add
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post #10 of 15 (permalink) Old 07-12-2016, 11:06 AM
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Quote:
Originally Posted by OVT View Post

My knee jerking reaction to threads like this is "don't fight your water". It is what it is - use what you got to your advanage. I strongly belive that stability is way more important then some specific number.
Tut! Tut! I know you made the exception to well water, but...

I've had that thrown at me more times than I care to count. What followed the good ol' "Stop chasing your pH' was lectures about how all well water is liquid rock so I should just shut up about it.

These are intelligent people slinging these words around and yet they couldn't wrap their brains around the notion that not all well water comes from the same place. Tell these how low the pH can get and suddenly they change their tune. I don't buy wild caught fish where some of them like that type of low pH. Even the filthiest tanks at Pet Co do not keep their tanks that low.

If I'm chasing my pH with water that has zero KH and a GH of around 1-2 out of the tap, that shouldn't matter to anybody. Layer this with what is deemed 'common knowledge' that all low tech tanks are never tested and are always left to a state of neglect ( I've read this far too many times around here alone lately) and it begs the question even further what difference does it make whether i chase my pH or not if this so-called knowledge is out there and is somehow fact? If I'm that negligent because I don't gas my fish with CO2 or use jugs of Excel, it shouldn't matter what I do as it will always be negligence.
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post #11 of 15 (permalink) Old 07-12-2016, 03:26 PM
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You are absolutely right @Smooch - what you do does not matter to me and is none of my business.
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post #12 of 15 (permalink) Old 07-12-2016, 03:51 PM
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I use crushed coral and I'm pleased with the results. I started with 4 tablespoons for a 45 gallon and increased the amount over many days until I had the KH and GH I wanted. I'm now at 12 tablespoons. I then adjusted my CO2 until the desired pH was achieved. I haven't changed the crushed coral for 2 months although I rinse it when I clean out my canister filter.
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post #13 of 15 (permalink) Old 07-14-2016, 11:11 AM Thread Starter
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Great opinions everyone.

This is a prime example of the aquarium world. Everyone does something different and it works for them. Every opinion is valid.

I am really starting to see that chasing a pH around is not the way to go (if you are within a certain, and quite wide, range. One point that many seem to agree upon is that stability is better.

How you obtain that stability may be different.

In my situation, where the KH hits 0, I'm concerned with pH constantly dropping, and potentially even crashing at night with the lack of CO2 absorption (keep in mind I do not inject CO2). Maybe this wouldn't happen because we are talking about such small amounts? Either way, in my head I'm thinking over time acid build up in a tank with minimal water changes will simply continue to drop. This is why I went with the crushed coral in the first place.
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post #14 of 15 (permalink) Old 07-14-2016, 05:01 PM
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A true zero KH is very unlikely to ever happen. Eventually the KH will be low enough that the plants can't use it, so the drop will stop. Any time you change the KH of the water you are using, whether with baking soda or calcium carbonate or any other form of carbonate, you will have to adjust the KH of the water you use for water changes. If you adjust it with baking soda it only takes a few minutes to arrive at a stable KH, but if you use a slow dissolving compound, like calcium carbonate, it may take days before the KH increases to where you want it, and then it may continue to increase beyond that.

Any KH will buffer the water against pH changes caused by weak acids like tannic acid, but it does not buffer against pH changes caused by dissolved CO2 (carbonic acid). In fact it is the combination of KH and carbonic acid that form the buffer - KH (carbonates alone) does not buffer the water at all. Atmospheric CO2 is always present to keep the concentration of CO2 in the water around 3 ppm, so that, plus the carbonates means your water is always buffered to some extent against other weak acids and bases.

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post #15 of 15 (permalink) Old 03-29-2017, 08:40 AM
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Buffering explained

In short, by adding crushed coral you add calcium bicarbonate (mainly) .... this acts as a buffer (helps maintain pH) ... if your pH is low (acidic) it will dissolve more of the crushed coral until it reaches an equilibrium, if you water was less acidic, less crushed coral would dissolve, that is why even when you added a lot, it did not increase the pH more (because equilibrium was already reached) More crushed coral just means it will last a lot longer (as long as you are still adding more CO2), by constantly adding CO2, eventually the crushed coral will all dissolve, since you are constantly adding more acidic compounds
it is also worth mentioning though, that when CO2 levels are high, more will dissolve out of the water (also because of equilibrium), since water can only hold so much dissolved CO2
If you are interested in the chemistry it is described below.

When adding CO2 to you water, you decrease pH (more acidic) because CO2 dissolves to form carbonic Acid, more then the natural 3ppm (as Hobby mentioned). This acid then dissociates to form bicarbonate [HCO3- (base)], and carbonate, CO3--.(also a base), the carbonic acid donates a proton (H+) to the water (H2O) to form a Hydronium ion [H3O+ (acid)] ....
These 3 chemicals act as a buffer.
when you increase CO2 concentration, the acid can react with the bases to form clean water, and when the pH becomes more basic, it can react with the acid to also form clean water.
Even normal 100% clean water (H2O) dissociates within itself (in small quantities) to form H3O+ (strong acid) and OH- (strong base). These 2 chemicals are constantly interacting to maintain pH of 7 (neutral)

Hope you found this informative and helpful
overall crushed coral (or any buffer substance) dissolves until equilibrium is reached... it acts to maintain pH, and
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