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It seems to me that pH moderation is constantly coming up as a  subject in just about every discussion.  Because it's such an important detail of all aquaponic systems, I thought that I'd start a discussion to let folks chime in on what has worked and what hasn't worked as far as controlling system pH.  I know that some of you will say that the subject has already been talked to death in other discussions, but I think that this will be a great resource for folks who don't have the time to wade through the other discussions to glean details.  So experienced aquapons (that means you- Aleece, Murray, Rupert, etc.), and anyone else with questions or advice:  let's make life easy for the newbies and share some pH knowledge.

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Ron, you are kinda worrying me.
Moving pH that fast with fish in a system is quite dangerous for the fish!!!!! And it can kill off bio-filter bacteria too.

What is the status of your cycling? Was the system just started? Had the bio-filter cycled up yet? Was there any sort of buffer on hand to control the pH as aquaponics naturally lowers pH over time.

Time of day that you take your pH readings can have an effect on the pH since over night algae will use of dissolved oxygen and put carbon dioxide into the water which will cause lower pH readings at dawn and through the day the algae will use up carbon dioxide from the water and give off oxygen so in the late afternoon the pH is likely to be much higher if you have any algae growing in the system.

Also, tap water can play tricky too check out my blog post for explanation on that.

With fish and bio-filter alive and functioning in a system it is best to only move pH one or two tenths per day. So long as there is no buffer in the system, aquaponics will naturally have a falling pH and once the pH gets down below 7, people usually need to add some shell grit or other self regulating buffer. My advise is usually, if the pH is above 7 leave it alone, it will come down naturally (if it doesn't, adding acid probably won't do much good because if there is a lot of some sort of buffer, adding acid will just cause pH bouncing.) If the pH is down near 6 add some buffer (calcium carbonate or shell grit) to keep the pH from getting so low that it can't be read accurately.
I'm still in the cycle but it is going extremely slowly. While there are some differences, I've been through this process in saltwater tanks (I used to run a pet supply biz focusing on aquariums, but that was 15 years ago). I've always pushed my PH adjustments a bit, usually in the .3 to .4 range in a day with no real problems ever encountered.

These swings were just out of the blue. I don't have an algae issue, so that won't be in the mix. My dissolved oxygen is extremely high (I don't have the numbers current but am pushing 70-lpm through a 9" membrane diffuser (6600 slits putting out 1mm-2mm bubbles).

I'll get it under control, just venting some frustration.

TCLynx said:
Ron, you are kinda worrying me.
Moving pH that fast with fish in a system is quite dangerous for the fish!!!!! And it can kill off bio-filter bacteria too.

What is the status of your cycling? Was the system just started? Had the bio-filter cycled up yet? Was there any sort of buffer on hand to control the pH as aquaponics naturally lowers pH over time.

Time of day that you take your pH readings can have an effect on the pH since over night algae will use of dissolved oxygen and put carbon dioxide into the water which will cause lower pH readings at dawn and through the day the algae will use up carbon dioxide from the water and give off oxygen so in the late afternoon the pH is likely to be much higher if you have any algae growing in the system.

Also, tap water can play tricky too check out my blog post for explanation on that.

With fish and bio-filter alive and functioning in a system it is best to only move pH one or two tenths per day. So long as there is no buffer in the system, aquaponics will naturally have a falling pH and once the pH gets down below 7, people usually need to add some shell grit or other self regulating buffer. My advise is usually, if the pH is above 7 leave it alone, it will come down naturally (if it doesn't, adding acid probably won't do much good because if there is a lot of some sort of buffer, adding acid will just cause pH bouncing.) If the pH is down near 6 add some buffer (calcium carbonate or shell grit) to keep the pH from getting so low that it can't be read accurately.
Ok Ron, Now that I know you have fish experience I'm not so worried, I couldn't tell from your profile how far along the system was or what your experience was.
You did mention hydroponics and some people who get into this from that side of things won't leave things alone enough to let them cycle.

Does your system have any sort of automatic top up? I know if I do a big top up from my well, it can pop the system pH up over 8 (my system is a pretty steady 7.6 most of the time because of all the shells in it.)

Cycling up an aquaponics system with fish in it can take 6-8 weeks and sometimes even more. I've done it fishlessly in 4 weeks.

Remember aquaponics is about patients, and then fish and plants.
No auto top up and pretty good water (it tested to 7.4).

It was just the swings for no apparent reason that was driving me nuts. I'll just take a hands off for awhile and let the cycle run it's course.

I am surprised at the time it takes. In the biz I could cycle a 150 gallon tank in two or three weeks with a single percula (clownfish) or Damsel. I have 35x that number of fish in a tank only 4x as large yet it will take 2 or 3x as long to cycle. I bel;ieve you, but can't help to wonder why.

TCLynx said:
Ok Ron, Now that I know you have fish experience I'm not so worried, I couldn't tell from your profile how far along the system was or what your experience was.
You did mention hydroponics and some people who get into this from that side of things won't leave things alone enough to let them cycle.

Does your system have any sort of automatic top up? I know if I do a big top up from my well, it can pop the system pH up over 8 (my system is a pretty steady 7.6 most of the time because of all the shells in it.)

Cycling up an aquaponics system with fish in it can take 6-8 weeks and sometimes even more. I've done it fishlessly in 4 weeks.

Remember aquaponics is about patients, and then fish and plants.
When I built my second system, I made a 1000 fish tank out of ferrocement. I make a mistake by not acid washing it thoroughly enough and the concrete leached into the water raising the pH. I started adding vinegar to lower pH but I had to add so much I began looking for alternatives. Vinegar has a very low% of acetic acid. I read on several forums to use citric acid. I began using granular citric acid and after about a week the entire system crashed. My net tank backed up with poop, the water got brown/smelly and all the roots got slimy. I did a little research on citric acid and discovered, to my horror, that it is actually an ANTIBACTERIAL!!!!!!! By using it, I killed my system and lost hundreds of plants. I moved my fish and drained the system and lined the concrete with a thick layer of paraffin. Since restarting the system I have not had a high pH problem.
I raise pH with calcium carbonate and potassium carbonate.
Wow, Chris. That is a horrifying story. I've been recommending citric acid to people in a list of ways to lower pH...so, ah, I think I'll stop doing that! Thanks for sharing - yikes

Chris Smith said:
When I built my second system, I made a 1000 fish tank out of ferrocement. I make a mistake by not acid washing it thoroughly enough and the concrete leached into the water raising the pH. I started adding vinegar to lower pH but I had to add so much I began looking for alternatives. Vinegar has a very low% of acetic acid. I read on several forums to use citric acid. I began using granular citric acid and after about a week the entire system crashed. My net tank backed up with poop, the water got brown/smelly and all the roots got slimy. I did a little research on citric acid and discovered, to my horror, that it is actually an ANTIBACTERIAL!!!!!!! By using it, I killed my system and lost hundreds of plants. I moved my fish and drained the system and lined the concrete with a thick layer of paraffin. Since restarting the system I have not had a high pH problem.
I raise pH with calcium carbonate and potassium carbonate.
I am loosing fish !!!!!! My tank is 340 gal, water temp 72 degrees, Ox 2-- 8 mg, Amonia 0.5 , No 3 - 40, No 2 -5,
Ph 8.5, Alk 180, Th 180, Cl- 0. My system has floating troughs just like Friendly and Chris Smith (my son). The water out of the tap has the same Ph, Alk & Th. I got 50 Tilapia fry in San Diego and they are doing fine, then I went to the desert and added 50-- 3 inch Fry about four weeks ago, these are the ones that are dying, one every couple of days. Help, is it the Ph and the Alk & Th???? or something else. My plants in the rafts are doing fine......Andy
No, it isn't the pH or Alk!!!! It is the Nitrite. NO2 is even more toxic to fish than ammonia is. Salt the system to at least 1ppt (1 kg of salt per 1000 liters of water) using non-Iodized salt (best to avoid table salt sine the anti caking agents are pretty bad too.) I usually use the cheapest solar pool salt or solar water softener salt I can get at the grocery store or hardware store. Make sure to dissolve it completely in a bucket of water before adding to the fish tank as undissolved salt crystals on the bottom of a fish tank can burn a fish that might rest against it. Tilapia are pretty rough but nitrite is to fish like carbon monoxide is to air breathers. The nitrite will bind with the blood in place of oxygen and keep the fish from getting the oxygen it needs. And then the fish dies of what many people call brown blood disease. Sodium Chloride helps mitigate this a little bit because the chloride ion will bind with the Nitrite and hopefully help keep some of the nitrite out of your fish. Stop feeding until both your ammonia and nitrite levels are 0. Add as much aeration as possible.

Andy Smith said:
I am loosing fish !!!!!! My tank is 340 gal, water temp 72 degrees, Ox 2-- 8 mg, Amonia 0.5 , No 3 - 40, No 2 -5,
Ph 8.5, Alk 180, Th 180, Cl- 0. My system has floating troughs just like Friendly and Chris Smith (my son). The water out of the tap has the same Ph, Alk & Th. I got 50 Tilapia fry in San Diego and they are doing fine, then I went to the desert and added 50-- 3 inch Fry about four weeks ago, these are the ones that are dying, one every couple of days. Help, is it the Ph and the Alk & Th???? or something else. My plants in the rafts are doing fine......Andy
Also do not try to adjust PH at this time. Too high of PH increases the toxicity of Ammonia, but lower PH increases the toxicity of Nitrite. Probably best to get the Ammonia and Nitrate in check, then worry about the PH.

Andy Smith said:
I am loosing fish !!!!!! My tank is 340 gal, water temp 72 degrees, Ox 2-- 8 mg, Amonia 0.5 , No 3 - 40, No 2 -5,
Ph 8.5, Alk 180, Th 180, Cl- 0. My system has floating troughs just like Friendly and Chris Smith (my son). The water out of the tap has the same Ph, Alk & Th. I got 50 Tilapia fry in San Diego and they are doing fine, then I went to the desert and added 50-- 3 inch Fry about four weeks ago, these are the ones that are dying, one every couple of days. Help, is it the Ph and the Alk & Th???? or something else. My plants in the rafts are doing fine......Andy
Aloha everyone
I read about all this pH trouble and wonder why I do not run into that problem. The pH of the water at my house from the tap is 7.0. I never have a problem (so far) with the pH wandering. It remains steady at about 7.2 to 7.4. The fish are well and the plants are growing very well. One other thing about my tap water it is not chlorinated. You think that odd I am sure but one well here in Waianae has no chlorine added to it. By the luck of the draw I get my from that one. I really need to check it each time I add water though. One time the man I used to get asian catfish from killed all his babies 20,000 because that day they put chlorine in the water. Better to be safe than sorry. The only thing I add to my water is the chelated iron,. I figure I need to add it about every 2 months. I begin to notice that the new leaves have a yellow color and I add the iron.. They green right up. I also never get the ammonia spikes. I guess that is because I have the fish in the tank for quite awhile before I put plants in the system. I usually add the plants gradualy. That is because I can't keep plants planted fast enough. Mahalo for all the good advice. I love this site
Raychel,
Sound like you just have a very well balanced system. Keep up the good work, it sounds like you are doing well with it. Part of the bigger trouble usually come when people start trying to adjust things and more often than not, they cause more problems than they fix.

If you water quality stays good and all you have to do is top up small (like 10% or less) amounts often, then even chlorine is probably not going to kill things (it is when you do larger than planned top ups or water changes that chlorine or chloramine can do major damage.)

Keep up the good work.
I am still loosing fish at the rate of one every two days. I don't think it is the water quality. I think there is something else going on. Any Ideas of diseases that I could have picked up from the second batch of 3 in fry that I got from Blue Beyond. Andy

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