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PH is a crazy thing, especially in aquaponics.

And this is why I do not even try to change it. These are two ph tests taken from two different systems, that use top up water from the same place. Actually the same hose. The only difference is that the one on the left came from my small system that runs off a 30 gallon aquarium, and the right is from my pond. 

The aquarium system has been running for at least 4 years now, and the pond almost a year.

Right now I'm tempted to take half of the hydroton from the little system and put it in the big system to see what that does.

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In aquaculture no two ponds no matter how similar, close together or how much they share resources and management are ever the same.

Fascinating! That's a big difference. I've wondered how much the PH could go down as the system matures here in AZ, since we do top off a lot and our water is, most of the time, pretty high PH. But this is far more than I would have expected.

If you don't mind me asking a few questions...

Is there anything at all that can be adding alkalinity to the pond? Any limestone or calcium stone?

How much do you top off in each tank (a larger percentage in one than another?), and what is your tap PH?

Yes PH is a crazy thing, adding hydrocloric acid lowers PH, careful not to much. I have developed a system that keeps my PH in check a little below 7. I havent found an optimum level though, some say 6.4 some say 6.8. Tilapia are definite diehard fish, in the beginning Ive had my PH go up and down wildly, it never affected my fish thank God.

The pond gets topped off more often and with alot more water, I think it has a volume of about 1500 gallons compared to just the 30 in the aquarium. I tested my top off tank tonight and it's exactly the same as the pond at about 8.4. We add about 50 gallons a day every day cause it never seems like we can get it full.

There may be small amounts of mortar in the pond. When we were putting the edging in place we may have dropped a little into it but we were very careful to wipe up any drops as we went. Also it gets a lot more dust and debris in it from any high winds that we get.

There was a time when the aquarium was as bright purple as the pond, like right after we moved from an apartment to the house and only brought half the water with us. It just seems to me that as a filter matures it manages to bring down the ph eventually. I'm hoping that in the winter when we don't have to top it off as much that we'll see a ph drop in the pond too.

Hi Stephanie

My pond never seems full here either LOL!  It takes about 2" of water every day this time of year     

My system always ran at 8.0 - 8.2 pH all the time with no issues except the veggies never looked happy.  I decided I should do something about and bought a 2 gallon package of Pool Acid (muratic acid)

I started adding 4 oz of pool acid with every hose fill; figuring I would eventually catch up with the pH, but I never got close...  I used most of the first gallon of pool acid (PA) before I decided to get serious; 4 oz/day was never going to get it over the hump.  But I really worried about shocking the fish

I got serious by adding 4 then 8 ounces of pool acid (mixed w/5 gal h2o) metered in with every pump cycle all day until I was well into the 6s on pH  at the end of the 2nd day!   Basically my entire 2nd gallon of PA when into the pond over about a 2 day period and none of the fish or plants are yelling at me yet. 

My advice is just Go For It! 

I am now adding 4-6 oz of PA with each and every 2" of H2O added in a 500 gal system to maintain the lower pH..  Therefore, I would be comfortable to start by adding 3 times that in your 1500 gal system or 12 -18 oz diluted in h2o and metered into the sump every 2 hours or so.  After the water has fully cycled a couple times to insure complete mixing check your pH.  Keep after it and you will eventually reach your goal and the fish and plants will be cool with it.  My pH is at 6.6 tonight!

I have found that Bashas' has PA for $9 for a 2 gal box, it you find a better price please let us know.

I am going to send you a friend request with my contact info if you want help or just a shoulder to cry on...


Regarding Pool Acid. Be sure to look on the bottle and check the concentration. It varies with the source. For example PA from some pool stores is as strong as 14% while from the supermarket it could be only 10% or less.

who knows something about raising prawn?  where to get them, what feed, is temperature critical, etc?

Dr. George is going to order some, but there's much to be learned about raising them. I don't think feed is an issue if they're raised in the AP system because they're scavengers & clean up some of the waste.

RE: Pool acid. Correction. Pool acid ranges from 14% to 35% HCl depending on the source. Be careful.

Thanks for the heads up on HCL % - so far everything I have purchased is 14.5%, but I will be keeping an eye on that for sure! 

Count me in on the prawn list!  Does anyone have any idea of the preferred pond environment for prawns is?

I'd love prawns.  Speaking of which, I am having an algae problem all of a sudden.  I can get the water clear but there is a thick accumulation of algae now.  This just occurred recently and I'm assuming it's the increase in the temperature and my tote does get direct sunlight for the first part of the morning and then one side has constant sunlight until later afternoon .  I have 3 algae-eaters but I can't even see them anymore, but I know they are down there somewhere.  I'm thinking prawns may do the trick....

Has anyone else experienced this problem here in AZ? 


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