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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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So, what is the problem?  If every thing is happy why are you not happy?  Are you hung up on a number?  Have you it let it run to see how far it will go?  Do you actually have a test kit to take you to 5.0?  If would really be nice to know just how low it is going.  You see, I have the same situation, but I have stopped letting it bother me.  As you said, "The fish are happy and the plants are happy"  Frankly, other nutrient problems would most likely be the cause of plants not reacting well.  In any case, I haven't a clue of how low it is going.  I just know that I have to add about 6 or 8 gals or water a day to make up for evaporation.  That additional water is running about 8.2 pH.  My total water capacity is somewhere around 350 gals.  The pH will spike if I add much more than that,  otherwise it pretty much seems to stay at the same level.  I think, since I can't test below 6.0  Some times it is better to just leave it alone.  You must strive for very subtle changes of just a few points (tenths) else you may be causing more harm than helping. 

"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".  

Incidentally, it is not uncommon for the morning pH to be different than the afternoon pH.  At night the fish are adding carbon dioxide to the water, after the plants get daylight they start consuming that carbon dioxide and giving off oxygen.  It will change the water chemistry.  If you are constantly trying to adjust it, you playing a guessing game.  If your system has the bacteria to keep cycling then your pH is likely not dropping as much as you think it is.  The overall average may be higher than an individual measurement.  Again watch for signs from your system.  My pH is a mystery, but my ammonia level is always within lower end of the scale, nitrites are zero and nitrates are generally running fro 5 to 20 as it varies on any given day and nothing is dying.  All this with high temps in 95 - 97 degree range.  I am pushing a lot of air through the fish tank to keep my DO up.

So, should I be concerned?

So, what is the problem?  If every thing is happy why are you not happy?  Are you hung up on a number?  Have you it let it run to see how far it will go?  Do you actually have a test kit to take you to 5.0?  If would really be nice to know just how low it is going.  

You see, I have the same situation, but I have stopped letting it bother me.  As you said, "The fish are happy and the plants are happy"  Frankly, other nutrient problems would most likely be the cause of plants not reacting well.  In any case, I haven't a clue of how low it is going.  I just know that I have to add about 6 or 8 gals or water a day to make up for evaporation.  That additional water is running about 8.2 pH.  My total water capacity is somewhere around 350 gals.  The pH will spike if I add much more than that,  otherwise it pretty much seems to stay at the same level.  I think that is the level, since I can't test below 6.0 I have no way of really knowing.

I think that some times it is better to just leave it alone.  I do know you must strive for very subtle changes of just a few points (tenths) else you may be causing more harm than helping. 

Incidentally, it is not uncommon for the morning pH to be different than the afternoon pH.  At night the fish are adding carbon dioxide to the water, after the plants get daylight they start consuming that carbon dioxide and giving off oxygen.  It will change the water chemistry.  If you are constantly trying to adjust it, you playing a guessing game.  If your system has the bacteria to keep cycling then your pH is likely not dropping as much as you think it is.  The overall average may be higher than an individual measurement.  Again I think one needs to watch for signs from their system.  My pH is a mystery, but my ammonia level is always within lower end of the scale, nitrites are zero and nitrates are generally running fro 5 to 20 as it varies on any given day and nothing is dying.  All this with high temps in 95 - 97 degree range.  I am pushing a lot of air through the fish tank to keep my DO up.

So, should I be concerned?

I can't answer for Dagmarvelous, but I guess in my case the problem with the numbers would be concern for my biofilter crashing. Apart from that, I'm happy. I just saw the post and thought I'd let Dagmarvelous know he/she wasn't alone. Sometimes that gives you the courage to stop worrying (or thinking your crazy) and keep going.

To answer your question, I purchased a small handheld pH meter to test my water since I suspected that the API Kit was not accurate enough. My tank drops by 0.2-0.4 pH units daily (when tested in the evening) and has gotten as low as pH 5.8 before I gave up seeing how far it would go in favor of saving my biofilter since I was seeing ammonia spikes and sickly looking plants at that pH. I test the pH twice a day and aim to counter the daily fall. If I am vigilant I seem to be able to do that, but that's not to say I'm correct in what I'm doing. I'm just learning.

 

I know where you are coming from.  It seems there are many answers and most are not the same.  I have gathered from the various threads that their are differences in each system that would make it act contrary to another.  I was on another thread dealing with high temps.  He had a 20K gal fish pool and hundreds of fish.  I have a 150 gal fish tank and a few Shiners and gold fish.  Do you think both systems would respond equally to the same stimuli?  He just had a major fish kill and he believes it was a result of deficient DO.  I am sure it would be considerably easier for me to run up my DO with a 150 gal tank that his 20000 gal pool.  Yet the chemistry on his system would probably be more consistent than mine.  It is crazy and there are just so many variables.  I guess the best any of us can do, is to do the best we can.  In fact, are not we all learning?  Some of us at the beginning and others more advanced knowledge.  The world of Aquaponics seems to be never ending and that was one of the attractions of becoming involved.  Good luck on your quest.
Casey Haas said:

I can't answer for Dagmarvelous, but I guess in my case the problem with the numbers would be concern for my biofilter crashing. Apart from that, I'm happy. I just saw the post and thought I'd let Dagmarvelous know he/she wasn't alone. Sometimes that gives you the courage to stop worrying (or thinking your crazy) and keep going.

To answer your question, I purchased a small handheld pH meter to test my water since I suspected that the API Kit was not accurate enough. My tank drops by 0.2-0.4 pH units daily (when tested in the evening) and has gotten as low as pH 5.8 before I gave up seeing how far it would go in favor of saving my biofilter since I was seeing ammonia spikes and sickly looking plants at that pH. I test the pH twice a day and aim to counter the daily fall. If I am vigilant I seem to be able to do that, but that's not to say I'm correct in what I'm doing. I'm just learning.

 

Update:  Well I let my mouth overload conventional wisdom and this morning my plants spoke to me.  I have a lot of funky looking leaves and spots on everything.  I was only having trouble with the cucumber plant but now it appears most if not all the plants are affected.  Root of the problem?  Well, I wish I knew for sure, but I believe it is related to pH.  I say that because we had a rain last night and this morning my nitrates also tanked.  I really must get me a device that will allow me to read below 6.0.  I think my bacteria might be laying back and taking a little time off.  I believe I just allowed that pH to run low for too long.  I had said I would just wait and see if my fish or plants would speak to me.  Well they are now screaming for help.  I added ten gals of high pH water which really never seems to do much by itself and a small amount of Ag lime (calcium carbonate).  I will give it a day of two to see how the water reacts.  The fish are fine and devouring the food I give them.  My ammo is running at about .5 now with zero nitrites and very close to zero nitrates.  It has done that before and bounced back the next day, but the plants have not shown any stress before.  Letting things run their course was not the best conceived idea that I ever had.  I thought things would adjust to the environment.  I know bouncing the environment around is not a good thing so why not the inverse?  The result is why not.  Still learning and having fun.

ok, testing your ph daily, you're likely to get 2 different readings because the ph will "swing" diurnally.. so for monitoring, take your test at the same time every day..

are you calibrating your ph meter? have you read any reviews of the device to see if other people find it inconsistant/inaccurate?

the api master freshwater kit is pretty reliable/accurate as long as you follow the instructions, and the reagents haven't expired..

very low ph is cause for concern, as this will affect the nitrifying bacteria

i would gradually increase ph with daily additions of hydrated/builders lime..add shellgrit to the growbeds (is the coral crushed very fine?)

what are you feeding the fish?

Very informative link! Thanks!! :D

Hi All,

Withholding, limiting feeding can be a relevant factor during cycling and its accompanying PH swings. This is one reason why I advocate fishless cycling. During this period(cycling) the bacterial colonies take time to "self-regulate" themselves until we can approach a daily dose regime of our buffers. With little to no ammonia in the system, even with fish present, its possible to move/raise PH a full point without doing much harm. Also its prudent to maintain a higher PH during cycling or even in mature/ish systems so as to avoid PH crashes. Its easier to recover a falling PH when you have more PH range. Also cycling in the presence of higher ammonia levels ensure an adequate bacterial population will be established. When the bacteria is affected/lost due to low PH's, recycling cost time/effort, and in the case of fish being present, causes them to have to endure yet another Nitrite spike. Keeping and maintaining a PH of say 7 during cycling will avoid falling to a reading of 6 which is out of the reading range of regular reagent kits, a reading of 6 may very well be lower. How much lower is anyone's guess.

Tradewind - Big Bummer! Sorry about the bump in the road, but I'm pretty sure you'll be able to turn it around. If it were me, I would stop feeding the fish until everything settles out, especially if you are seeing an ammonia spike. Good luck!

Keith - I do take into account pH swings at different times of the day. I make my additions based on the evening reading and check "approximately" how much the pH changed in the morning so I can get a gauge on how my additions are affecting things. 

I calibrate the pH meter with a 7.0 standard once a week. It is a handheld water resistant meter from HM Digital. I am not sure how accurate others have found it to be, but pH meter accuracy has a lot to do with maintenance, calibration, age of the meter, build-up on the exchange surface of the probe, etc. so I am not sure how much stock I would put it reviews on a meter which is generally used by the average joe (since it is by no means a high end meter) since the average joe may or may not know how to properly use or care for a pH meter. It is my understanding that as long as a meter is appropriately maintained and calibrated that it should be more accurate than a color indicator in measuring pH. Checking against known standards is the best way to assess accuracy, but this can be expensive since the standards start to degrade as soon as you open them and who can afford to be buying standards all the time? I have been comparing the results I get on the handheld meter to the API test kit pH and have found the following results for my tank:

Handheld meter pH range 5.8-6.0 correlates to API Kit pH of 6.0.

Handheld meter pH range 6.1-6.7 correlates to API Kit pH of 6.4

Handheld meter pH range 6.8-7.0 correlates to API Kit pH of 6.8

(My API kit doesn't expire until Oct 2017. I checked when I saw the above differences.)

For my situation anyway, it seems that this would indicate that more is going on than the API test is able to tell me. My additions are very small and are only an attempt to counter the daily drop in pH I see, not to hit a specific number. I have a 175 gal tank and am adding 1/2 tsp of a 50/50 mix of calcium carbonate and potassium carbonate with each addition (usually once daily). This seems to get me anywhere from 0.0-0.2 pH unit increase. Occasionally I will need to add a second 1/2 tsp 12 hours apart. So far this has worked for me, but I am no expert and this probably will not work for anyone else's set-up (so don't take my addition rates to be any sort of guideline and subsequently kill your fish).

I am experimenting with shell grit because I would like to be able to get away from my tank for a couple days without it going below 6.0 and crashing my biofilter. No luck so far....the local aquarium store told me to dump a whole 5 lb bag of shell grit in the bottom of my tank, but something tells me that would not be wise. I put a large handful of shell grit in an old pantyhose leg and dropped it in the tank so I could pull it out again if I needed to. I am slowly increasing the amount.

I feed the fish AquaNourish fingerling feed. I hope that answers all of your questions!!!

Harold - I agree!

Great discussion!

I was wondering if I was feeding my fish enough. Frankly, that might be a major contributor to the problem.  When I was bringing my system through cycling I did fishless adding a cap or two of ammonia.  It was very easy to regulate and I cycled in about 4 weeks.  My ammonia would be back to zero the next morning with zero nitrites and a boat load of nitrates.  I am wondering if my little fish are putting enough into the water to do anything.  Perhaps the little ammonia I am seeing is due to fish kill which seems to be pretty normal for these Shiners.  They really do dislike 97 deg water.   But they have lived considerably longer than I was told they would by the guy that sold them to me.  I still have about 20 of the little guys in there.  I was thinking maybe a should feed them a bit more.  They boil the water when I do sprinkle a little food in there and it is gone is just a few seconds.

Hi Tradewind,

May i suggest, if you'd like we can carry the discussion of your system/issues to a separate post/topic, which can be dealt with in detail. This way we won't color/distract from the information coming out of Dagmarvelous's discussion.

Tradewind said:

I was wondering if I was feeding my fish enough. Frankly, that might be a major contributor to the problem.  When I was bringing my system through cycling I did fishless adding a cap or two of ammonia.  It was very easy to regulate and I cycled in about 4 weeks.  My ammonia would be back to zero the next morning with zero nitrites and a boat load of nitrates.  I am wondering if my little fish are putting enough into the water to do anything.  Perhaps the little ammonia I am seeing is due to fish kill which seems to be pretty normal for these Shiners.  They really do dislike 97 deg water.   But they have lived considerably longer than I was told they would by the guy that sold them to me.  I still have about 20 of the little guys in there.  I was thinking maybe a should feed them a bit more.  They boil the water when I do sprinkle a little food in there and it is gone is just a few seconds.

your bacteria will begin to die at 6.0 and under.. don't ride that low if you can help it.

I use river rock to control pH and haven't adjusted in over 3 years.. go with about 30% of your media volume, use 3/4" river rock (not pea gravel). once it starts to work, you need to pull the shell out of the sump.

 

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