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pH continually dropping to 5... What the heck is it??

My system is 6 months old and the pH has been dropping since day 1! I can't figure it out and it's driving me bonkers. No dead fish, no dead spots, I even replaced a bed that had pond-liner cuz I thought it might be the culprit. Nope, still dropping! It wants to go below 5! Plants seem happy, I get great squash but mushy tomatoes. And a gigantic pumpkin that is very happy. Fish seem fine as they are eating and making babies, but the fry will die if it gets too low.

Water out of the tap is fairly hard, and 8.3 (after sitting a few days in a barrel). I also have a breeding tank (no plants) and pH stays right around 8. But in the outdoor AP system, it drops. I even have 30lbs of crushed coral in the beds and sump. At this point I'm adding a tablespoon of pHUp almost every day. I've read tons of posts, been patient, but I'm at my wit's end. Help please!

Here's the low down:
CHIFT PIST System
275 gallon Fish Tank
with 30 6" fish and usually some fry
60 gallon sump
3 Growbeds 4'x4'x12" with Hydroton

Temp is 74
Ammonia .25
Nitrite 0
Nitrate 0-5 (closer to 0)

Any ideas? Could it be the Hydroton?

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UPDATE:  It has been a couple of days since I treated my system with Ag Lime (Calcium carbonate); the same stuff Nate Storey says to avoid.  However, my pH is a 6.0 or below (my kit does not go any lower), Ammo .25, Nitrites 0 and Nitrates 40.  What!!  How can that be isn't the cycle suppose to break down with low pH?  Nate says we should be running our system at 6.0 to 6.4 Nate's Video on pH.  

He also says to avoid the carbonates, but yet most of the suggestions we read here are saying to add carbonates such as Coral, eggshells, lime (hydrated lime is an exception), and lime stone.  Some say it has balanced their system and is virtually self maintained and I have no reason to not believe them. 

As someone new to AP I find it is really difficult to know what to do.  So I just did what I did and the results and coming in on a daily basis.  I still feel uneasy about such a low pH.  But the plants are happy again and my fish seem to be thriving.  The water I add to my system is a pH of 8.2, but the pH doesn't seem to last very long.  So I need to know the actual hardness of the water to see if it is buffered enough to prevent the drop or if something else is causing it.  I certainly need to check that before I consider adding any additional Calcium Carbonates.

Anyone have any input as to how you see it?

Tradewind - I watched the video you referenced. What I took away from it was that Nate was advising caution regarding carbonates. If your system is at 6.0 or above then it is best to not use carbonates unless you really understand the chemistry behind what your are doing or you can do more damage than good. He did advise very judicious use of carbonates in systems that hang out below 6.0 like ours tend to want to do.

I added shell grit at the dose Wes recommended and have not had to adjust the pH for two days now. I plan to remove the shell grit tonight as Wes recommended so that I don't do more harm than good until I understand the chemistry in my tank better.

I think we have probably stretched this discussion as far as anyone "in the know" is willing to go with us. Now we have to take the really good concepts presented by Keith, Harold, Alex, Randall, Wes, and Rob and do our own research, learning, and experimentation like they did. That is what made them successful in the industry and what make us Newbies after all!

I personally think the key to balancing my low pH system lies in balancing calcium, KH, GH, mineral cations/electrolytes, and redox which is way more complicated than can be covered in a discussion forum. I think the articles I attached earlier are a decent start in the right direction though and I plan to hit up the library soon. Good luck with your system!

Thanks to all who contributed to the discussion. I learned a ton and I am off to the races so to speak!

Just know that your system will only use the calicum at the rate it needs and thus your ph will level out. If you take the coral out the system it will naturally start to go acid again and the ph will start to drop.
 
Casey Haas said:

Tradewind - I watched the video you referenced. What I took away from it was that Nate was advising caution regarding carbonates. If your system is at 6.0 or above then it is best to not use carbonates unless you really understand the chemistry behind what your are doing or you can do more damage than good. He did advise very judicious use of carbonates in systems that hang out below 6.0 like ours tend to want to do.

I added shell grit at the dose Wes recommended and have not had to adjust the pH for two days now. I plan to remove the shell grit tonight as Wes recommended so that I don't do more harm than good until I understand the chemistry in my tank better.

I think we have probably stretched this discussion as far as anyone "in the know" is willing to go with us. Now we have to take the really good concepts presented by Keith, Harold, Alex, Randall, Wes, and Rob and do our own research, learning, and experimentation like they did. That is what made them successful in the industry and what make us Newbies after all!

I personally think the key to balancing my low pH system lies in balancing calcium, KH, GH, mineral cations/electrolytes, and redox which is way more complicated than can be covered in a discussion forum. I think the articles I attached earlier are a decent start in the right direction though and I plan to hit up the library soon. Good luck with your system!

Thanks to all who contributed to the discussion. I learned a ton and I am off to the races so to speak!

Casey,

I think you have pretty well summarized all that has occurred and aptly attributed to those who pointed us in the right direction.  Discerning that direction is a whole "nother" issue.  Wes's caution was heeded before it was given on my part as I knew a boat load of carbonates would not be wise in the least.  The bit about our pH leveling out, is what we all seek.  I still do not think it should be all that complicated unless we shoot ourselves in the foot.

Since you have closed the lid on the coffin, I think it is time to bury this puppy and go on with the next challenge. 

Casey Haas said:

Tradewind - I watched the video you referenced. What I took away from it was that Nate was advising caution regarding carbonates. If your system is at 6.0 or above then it is best to not use carbonates unless you really understand the chemistry behind what your are doing or you can do more damage than good. He did advise very judicious use of carbonates in systems that hang out below 6.0 like ours tend to want to do.

I added shell grit at the dose Wes recommended and have not had to adjust the pH for two days now. I plan to remove the shell grit tonight as Wes recommended so that I don't do more harm than good until I understand the chemistry in my tank better.

I think we have probably stretched this discussion as far as anyone "in the know" is willing to go with us. Now we have to take the really good concepts presented by Keith, Harold, Alex, Randall, Wes, and Rob and do our own research, learning, and experimentation like they did. That is what made them successful in the industry and what make us Newbies after all!

I personally think the key to balancing my low pH system lies in balancing calcium, KH, GH, mineral cations/electrolytes, and redox which is way more complicated than can be covered in a discussion forum. I think the articles I attached earlier are a decent start in the right direction though and I plan to hit up the library soon. Good luck with your system!

Thanks to all who contributed to the discussion. I learned a ton and I am off to the races so to speak!

Ok, maybe I won't take it out then.It has been so nice to have it be stable!! Thanks again!

Hey that was way too quick with the adjustment but glad to hear. Just keep checking on the ph for at least a month or so to make sure things are going the way you want. I have to say I love the fact my system stays at 6.8 tp 7.0 and I don't have to do a thing but keep and eye on it by doing my regular water tests. Glad I could help.

Wes,

I think your comment was directed at Casey about being way too quick. being that his system balanced that quickly after only two days.  That does present an interesting question though.  If we have been having low pH problems and we make an adjustment with some form of carbonate and then see results in a short order, what is the explanation?  We all know that it takes time for these changes to occur as the absorption of the minerals is a gradual process.  Basically the same thing happened to me with adding Ag Lime, a change in the short run but then a return to a lower level and then again a return to a higher level after waiting longer yet.  Are we seeing a reaction to the finer particles and then a reaction the coarser particle size as it is absorbed?  Unlike bicarbonates that react quickly and then burn off quickly it was my thinking the other forms of carbonates would be more gradual and offer consistency, else why do it?  Am I in the woods here?

wes said:

Hey that was way too quick with the adjustment but glad to hear. Just keep checking on the ph for at least a month or so to make sure things are going the way you want. I have to say I love the fact my system stays at 6.8 tp 7.0 and I don't have to do a thing but keep and eye on it by doing my regular water tests. Glad I could help.

I'm so glad I started this discussion!  I am learning so much just "watching" you guys talk!

Thanks!!

Update:  Just another chapter in the adventure:  Last night we had a really heavy rainstorm pouring a lot of water into my AP system.  I am not sure I understand how these things occur, but yesterday afternoon my pH was running abut 6.8.  This morning it is at 7.8.  Now that really confuses me.  I was under the impression that rainwater was pH neutral or 7.0.  If my pH was running 6.8 why would the addition of copious amounts of rainwater run it past 7.0?

Yes it has been my experience that added calcium in the form of hydrated lime  does change the ph quicker and it also doesn’t last as long. That is the beauty of the crushed coral or bed rock that Rob Nash was talking about. After you find out the amount that your system needs it balances itself out. The ph usually levels off at 7.0. In a healthy system the coral keeps the ph balance in check by only dissolving the necessary amount when the Ph starts to drop and only then.

Wes,

In regards to Hydrated Lime I have found the following information in various placing on the internet and I have summarized here:

Calcite, sea shells, coral, aragonite and vaterite are pure calcium carbonate minerals. Industrially important source rocks which are predominantly calcium carbonate include limestone (ag lime), chalk, marble and travertine.  As you can see calcium carbonate (CaCO3) and it comes from nature.

Hydrated lime on the other hand is Calcium Hydroxide (Ca(OH)2) and mostly comes from an industrial process whereas water is mixed with Calcium Oxide CaO.  The mineral form, portlandite, is relatively rare but can be found in some volcanic, plutonic, and metamorphic rocks. It has also been known to arise in burning coal dumps. (end of reference)

For the most part,  I believe we have been discussing the addition of various forms of Calcium Carbonates (CC) such as the shells, and crushed coral and limestone and marble were a few that was mentioned.  So to keep it on point, I would prefer to avoid the discussion of Calcium Hydroxide which is a different story altogether.  In fact, Nate makes a very clear distinction between the two and that is another topic I would rather avoid.

For the moment let us concentrate on the use of calcium carbonates and their response.  Now back to my question, which was not addressing the new addition of CC but rather the influx of rainwater.  Why would a system that had been buffered with CC and was holding at 6.4 range spike to 7.4 with the addition of rainwater?  Now in truth the answer could well be in my inability to differentiate between 7.2 and 7.4 on the color chart.  I have read elsewhere that CC would hold to a upper limit of 7.2.

What ‘cha think?


wes said:

Yes it has been my experience that added calcium in the form of hydrated lime  does change the ph quicker and it also doesn’t last as long. That is the beauty of the crushed coral or bed rock that Rob Nash was talking about. After you find out the amount that your system needs it balances itself out. The ph usually levels off at 7.0. In a healthy system the coral keeps the ph balance in check by only dissolving the necessary amount when the Ph starts to drop and only then.

I am not sure what is going on with your system. Rain water mixes with carbon dioxide in the air (and pollutants) as it falls which makes it slightly acidic, so it seems unlikely that the rainwater would make your system more basic. As Wes mentioned, the CaCO3 should dissolve (or not dissolve) based on pH (it starts dissolving under pH 7.0 [approximately] and stops dissolving above pH 7.0 [approximately]) so it seems unlikely that it would make your system more basic than ~7.2.

You and mother nature have made several changes to your system over the last few days....you may just want to let it settle out and see what the pH is in a day or two before you think about making any other changes. The only other thing I can think of would be testing errors. Sometimes if a test tube doesn't get rinsed out well and there is a little bit of reagent left from a previous test it can give an incorrect pH result (I've had that happen). When in doubt, retest! Also, as mentioned above there can be differences in pH depending on time of day. I'd keep checking it daily at the same time until you see what it settles out at.

 

 

 

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