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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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ph will drop from the nitrification process.. you need to buffer it back up, but slowly..

i'd start with a little hydrated lime, but add shellgrit to your growbeds (some folks will put the shellgrit in a bag/stocking and hang in the ft) to gradually increase the ph to around 7.2 to 7.4

Thanks for your insight Keith, I was afraid no-one would reply!  I do have about 10lbs of crushed coral mixed amongst the hydroton in the growbeds, and then another 15-20lbs in a mesh bag sitting under where the beds drain so there's plenty of water movement over the bag.

I was alternating between hydrated lime and pHup, but the hydrated lime seemed to have very little effect.  Maybe I need to add a larger amount??  I'm just afraid to do it too quickly.  

It's very severe... I mean, I will get it up to 6 over the course of a day, and it will drop to 5 the next morning.  It's been going on like this for months, which can't be healthy.  And I'm getting a little discouraged.  Do you think it could be the hydroton?  I havent' seen much, but I did see one post where a guy thought it could be his hydroton. I know it doesn't make any sense, but I only have pvc, hydroton and IBC totes which were previously used in a AP set-up by a trusted friend.

Hi Dagmarvelous,

Please re-read Keith's reply. Whats happening to your PH is normal and expected. Some AP'ers add a buffer(carbonate) as a daily dose. Some dose twice a week, once per week etc. The process of converting fish feed into plant feed means that your PH will decline daily, so you'll need to maintain a level by buffering.

it's not from the hydroton, (unless you got some kind of crazy hydroton substitue!) coral will act very slowly, much like the shellgrit.. and if it's not ground very fine it will take longer (more surface area) to affect the system

if you need that much buffer, it's best to alternate between a calcium and a potassium compound (and i'd not use the "ph up product, sorry)

 

you will have a ph swing daily! (diurnal)  so check at the same time every day so that you'll have a more accurate record of what the ph is doing..

OK, I get where you are coming from.  But it sounds like your system is just going through the pains to get cycled.  I would think you would have higher levels of nitrates if you were cycled and processing the waste of 30 fish even small ones.  Have you taken readings at different times of the day.  It is not uncommon for the Ph to build in the night and drop after the plants start consuming the carbon dioxide.  Something seems out of whack.  If nitrites are 0 and you are converting your fish waste, I would think you nitrates would be a bit higher.  If you system is not converting the waste then why are the ammonia levels at only .25?

.I am not sure I would use Hydrated Lime as it is caustic, Calcium Carbonate (agricultural lime) is safer.  There are some that say to stay away from carbonates as they cause a control program.  But the other side says, not so.  In fact, they say, using Calcium Carbonate which qualifies as Organic creates a more stable system.  You can get any opinion you want if you look long enough.

My system is on the very cusp of being cycled and my Ph was always dropping.  I started using Sodium Bicarbonate only because it was safe and I had it on hand.  I have discontinued that practice sense having to add it often would build up the Sodium in my system.  I began using Agricultural Lime, (Barn Lime some call it), mostly because it easily available and is a buffer rather than an adjuster.  Now I can generally keep it in range with additions of water as it is a high Ph water source.  Once cycled I believe you can run with a lot lower Ph than some say you need.  

I know I didn't answer your question, but hopefully I have shared enough of my personal experiences to help you figure it out.  There are so many variables that sometimes it is much like a guessing game.

Thank you all for the input!  Even though my problem has not been solved, you have given me the confidence that I'm not totally whacked out with what I'm doing either!

I waited and watched for over 6 months, knowing full well that patience is key in AP.  I figured that my system WAS fully cycled, after all it's been months.  And yes, I always do my testing in the morning.  Should I wait until evening, after the plants have been at work all day?

Regarding the Hydrated Lime... several folks have recommended it.  Most say to alternate between that and the pH Up.  What to believe?  What to believe?  Are there long term negative effects from using Hydrated Lime?  It's caustic?...yikes!!

Hydrated lime isn't caustic once it's in the water though. I don't use it in my system, but I use it for pasteurizing straw for mushroom bags. It's not terribly caustic, I've gotten it on me before with no problems. But yeah, I wouldn't use it for chalking my hands.

I'm sure adding calcium to your system would be a plus for calcium carbonate.

Personally, my pH is so high naturally, I've never needed to make an upward adjustment. Except for one time where I swung it too low and yeah, pH Up works just fine and dandy.

Tradewind said:

OK, I get where you are coming from.  But it sounds like your system is just going through the pains to get cycled.  I would think you would have higher levels of nitrates if you were cycled and processing the waste of 30 fish even small ones.  Have you taken readings at different times of the day.  It is not uncommon for the Ph to build in the night and drop after the plants start consuming the carbon dioxide.  Something seems out of whack.  If nitrites are 0 and you are converting your fish waste, I would think you nitrates would be a bit higher.  If you system is not converting the waste then why are the ammonia levels at only .25?

.I am not sure I would use Hydrated Lime as it is caustic, Calcium Carbonate (agricultural lime) is safer.  There are some that say to stay away from carbonates as they cause a control program.  But the other side says, not so.  In fact, they say, using Calcium Carbonate which qualifies as Organic creates a more stable system.  You can get any opinion you want if you look long enough.

My system is on the very cusp of being cycled and my Ph was always dropping.  I started using Sodium Bicarbonate only because it was safe and I had it on hand.  I have discontinued that practice sense having to add it often would build up the Sodium in my system.  I began using Agricultural Lime, (Barn Lime some call it), mostly because it easily available and is a buffer rather than an adjuster.  Now I can generally keep it in range with additions of water as it is a high Ph water source.  Once cycled I believe you can run with a lot lower Ph than some say you need.  

I know I didn't answer your question, but hopefully I have shared enough of my personal experiences to help you figure it out.  There are so many variables that sometimes it is much like a guessing game.

My suggestion to you is to just Google it up.  You will find some people who say carbonates are bad therefore use Hydrated Lime (Calcium Hydroxide) Builders lime it is all the same,  others say no, no, don't use that stuff it does not qualify your system as Organic instead use Agricultural Lime (Calcium Carbonate), Barn Lime whatever it is all the same.  another option is Potassium Hydroxide.  Nate Storey says to alternate between the last two or use 50/50 of each.  Read what you will and make a decision.  After all, you are the one who will have to live with that decision.  Frankly they all pick your pH up, in fact, if you just wanted a quickie fix use Baking Soda.  Don't keep using it though as it is a sodium and will build up salts in your system.  I have used it several times and it works as good as any.  Now I just add treated tap water as it is about 8.2 pH, but I have to be careful I don't add more than about 6 or 8 gals as it will pick it up too quickly.  A large adjustment of your pH say more than a few tenths can cause stress to your fish.  Sometimes it is best to do nothing until either your fish or your plants speak to you.  My system pretty well runs under 6.0 don't know how much cause my kit stops there.  But after treatment with a few more gallons of water than I should it is just into the 7.0 pH.  That is too much because it is at least a full point of change.  Small change, if any change at all, is what you seek.

Dagmarvelous said:

Thank you all for the input!  Even though my problem has not been solved, you have given me the confidence that I'm not totally whacked out with what I'm doing either!

I waited and watched for over 6 months, knowing full well that patience is key in AP.  I figured that my system WAS fully cycled, after all it's been months.  And yes, I always do my testing in the morning.  Should I wait until evening, after the plants have been at work all day?

Regarding the Hydrated Lime... several folks have recommended it.  Most say to alternate between that and the pH Up.  What to believe?  What to believe?  Are there long term negative effects from using Hydrated Lime?  It's caustic?...yikes!!

I bought a 40 lb bag of Barn Lime (Calcium Carbonate) at Tractor Supply for 2 bucks.  I couldn't believe it.  It cost me more to drive there than what the product costs.  Considering I use half of a 3/4 PVC elbow as my measuring device, how many lifetimes do you think it will last?

Randall Wimbish said:

Trade wind.  I must say,  That is a pretty good summary.   I will ad, You can buy a 40 or 50 lb. bag of type s lime "builders lime" at home depot for about eight bucks and some change. Then you will need about three or four five gallon buckets with lids to store it in.  That will last a very long time for a small system.  I found potassium hydroxide on the web for very cheap.  In fact shipping out weighed the cost of 4 lbs of potassium hydroxide but I now have it and use it in moderation.  Hydroponic stores sell it very diluted an a bottle called p'h' up for way more than the flaked version available online. You can buy a 40 lb. bag of pool salt at leslies pool supply for around eight bucks as well and it is the same thing as aquarium salt sold for more that eight bucks a lb. with the "aquarium" name on it.  And a little bit of Epson salt goes a long way also but available in 50 lb bags for cheap if you look around if you need that much and last but not least I think you suggested it in a previous thread but, some limestone pea gravel or river rock mixed in your media might work for you as well..

I have the exact same problem, so you are not alone! I have a 175 gal tank with a single grow bed that sits above the tank. I started cycling back in May. The local water here is pH 8.2, but within one week of starting cycling it was down to 6.0 and dropping and I have struggled to keep it around 6.5 ever since. The local water apparently has no buffering capacity whatsoever. The fish don't seem to be to disturbed by it (so far) and the plants seem fine. I check the pH twice a day (morning and evening) and make small adjustments with a 50/50 mix of potassium carbonate and calcium carbonate once or twice a day. It's a pain in the neck for sure. I am currently experimenting with shell grit in the hopes of getting the system to be a bit more stable...so far with no effect. I'd be curious to know how things go with your system and if you find a good solution because I'm in the same boat!

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