# How long will it take crushed coral to buffer PH



## KlintD

I purchased a used 75g tank that came with probably 150# of crushed coral as substate (it was 6'' deep in places!!). When setting up the tank I removed some and now have an average of 2 inches over the entire bottom of the tank. It has been up and running for almost 2 weeks. The PH of my tap water is 7.2 and after a week and a half the PH of the aquarium water is 7.4

Anyone have experience with the amount of time it takes for substrate to influence water conditions?

Does crushed coral lose some of its ability to buffer the older it gets?

Are there different types of crushed coral that have different buffering capacities?

Note when setting up the tank I did not rinse the coral with a hose but I did gravel vac it a couple times when filling the tank.


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## Steveboos

I believe it will leech out over time, but it has to be a LONG time. I would venture to say that if you put some in a filter bag inside your HOB or Canister, it would probably help more than waiting for the substrate to raise the Ph that much.


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## KlintD

Steveboos said:


> I believe it will leech out over time, but it has to be a LONG time.


Interesting, so combine this with weekly water changes and I would guess that using crushed coral as a substrate is not the best solution for buffering.


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## newforestrob

I think your fish will adapt to your ph,as long as it is steady,my experience is having a high ph,but a low kh,where my ph lowered,in between water changes,my fish would flash and quiver,
check your kh,if it takes around 9 drops,to change color,I wouldnt mess with anything


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## KlintD

Thanks for the replys. I know there are two camps on buffering, do it and dont do it, and they dont see eye to eye. My question is not to buffer or not. My question was more aimed at trying to find out how crushed coral as a substrate impacts PH. Based on my experience and Steveboos' comment it looks like if someone was wanting to buffer there might be a better method.


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## halffrozen

Either dosing or some PH raising rock...


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## newforestrob

I add baking soda,I change alot of water,I dont think limestone rocks or coral sand would leach fast enough to make a difference


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## Mike_G

Crushed coral is more useful for *resisting* change in pH than actually raising it- I also use baking soda.


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## 13razorbackfan

Usually you should see a spike in kH within 24hrs or so after adding crushed coral. Adding crushed coral increases the buffer capacity of the tank via the kH. As your kH rises so will your pH. Any increase in acidity should dissolve some of the crushed coral keeping the water buffered. If the crushed coral was used when you bought the tank the buffering capacity may be diminished and you may need to remove the old and add the new. Some pieces of the coral may erode faster than others using up the calcium carbonate that is needed to alter the pH.

Now...if the water being added to the tank during water changes is as hard as the water existing in the tank after buffering capacity has been reach via leaking out of calcium carbonate then the crushed coral could last a really really long time...certainly much longer than anyone of our lifetimes. However...if the water you are adding in is more acidic than the water being replaced it depletes the calcium carbonate in the coral much faster than would happen normally in nature.


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## Nodalizer

If you want it to buffer at all you would need it in your filter, not your substrate. It won;t break down much unless the ph falls. Using water flow can cause it to errode adding buffers.


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## 13razorbackfan

Nodalizer said:


> If you want it to buffer at all you would need it in your filter, not your substrate. It won;t break down much unless the ph falls. Using water flow can cause it to errode adding buffers.


Yep...and the increased oxygenation running through the filter helps. If your water is acidic then replacing the crushed coral in your filter depends on how quickly the calcium carbonate is used up so regular testing is needed to keep up with how often it needs to be replaced.


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## jackskellington101982

Might I ask a question. Do you have any drift wood in the tank? if so that could keep the Ph a little lower. Other than that. What every one else has sugested is about right. I use crushed coral in my tank and still manage to keep my ph at about 7.2 with the driftwood in it.


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## Nodalizer

Just a side note, driftwood won't lower ph any noticable amount unless its leeching tannins, so the tank is a brownish color, like in a neon tank or similar.


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## KlintD

The crushed coral was in the tank when I purchased it. I dont have any details about the acidity of the previous owners water.

I am not trying to buffer the water and raise the PH I just thought the results were interesting as I thought the PH and KH would be higher than they are now. A couple more stats on the setup:

- Footprint of the tank is 48X18 
- I have two canister filters each pushing over 250GPH with spray bars on each return. 
- There is a decent amount of current over the coral so I would assume CC could leech out
- No drift wood in the tank, only a couple fake rocks and a fake plant
- My tap water is 7.2 PH (dont know the KH right off hand)

After a week with water in the tank my PH is 7.4, I was guessing it would be higher than that. Not sure how much but somewhat higher.

Just because I am curious I am going to attempt to put some coral in the media basket of my cansiter to see what happens to the PH and KH readings.


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## 13razorbackfan

KlintD said:


> The crushed coral was in the tank when I purchased it. I dont have any details about the acidity of the previous owners water.
> 
> I am not trying to buffer the water and raise the PH I just thought the results were interesting as I thought the PH and KH would be higher than they are now. A couple more stats on the setup:
> 
> - Footprint of the tank is 48X18
> - I have two canister filters each pushing over 250GPH with spray bars on each return.
> - There is a decent amount of current over the coral so I would assume CC could leech out
> - No drift wood in the tank, only a couple fake rocks and a fake plant
> - My tap water is 7.2 PH (dont know the KH right off hand)
> 
> After a week with water in the tank my PH is 7.4, I was guessing it would be higher than that. Not sure how much but somewhat higher.
> 
> Just because I am curious I am going to attempt to put some coral in the media basket of my cansiter to see what happens to the PH and KH readings.


Sure...let us know what you find.


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## KlintD

A couple of notes about my previous findings. I was doing water tests with 5 in 1 test strips now I have an API kit. 
- The 5 in 1 test strips said my tap water is 7.2 PH, the new test kit says my tap water is 7.8 PH. 
- The 5 in 1 test strips said my aquarium water was 7.4 PH, the new test kit says it is 8.1 PH.

I added some of the crushed coral to a bag and placed it in my canister filter. It is an XP2 (300 GPH), not sure if it matters but I added the coral just before the final micro filter pad.

After 2 days with the coral in the canister the PH is the same 8.1
After 3 days with the coral in the canister the PH is the same 8.1

My preliminary conclusions are:
- It takes longer than 3 days to see any change in PH
- I didnt add enough coral to the filter to make a difference for a 75 gallon tank
- There is no difference between coral in the filter or used as a substrate

In order to prove out the final possible conclusions I will be removing all my coral substrate soon and replacing it with sand. I will be testing the water to see if the coral in the filter can maintain an 8.1 PH level.


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## KlintD

So, I removed all the crushed coral substrate and replaced it with sand. I added about 5 pounds of the crushed coral back mixed in with the sand. I added 100 lbs of sand so the sand to coral ratio is 20:1

Note when I changed from coral to sand I did a 100% water change.

It has been a week since I made the change. I have done 2 PH tests over the week the and it is holding at 8.1. Note this (8.1) was the same value as when I had 100 lbs of crushed coral substrate. I also had a reading of 8.1 when I had crushed coral substrate and a bag of coral in my canister filter, and now 8.1 with only a bag or coral in the filter.

My tap water is 7.8 so the coral isnt moving the PH much at all. Adding a large amount doesnt seem to have any greater impact than a small amount in a canister filter.


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