Backyard Aquaponics
A place to discuss aquaponics

Hi Peoples!

Ive been cycling my system now for a few months and found I was over feeding because the nitrates were off the scale of 160ppm.

pH is also uncomfortably high at 8.2

Plants are now showing signs of iron def. I'm assuming because of the high pH.

I did have limestone in the sump tank but removed it about a month ago.

I have been doing water changes and adding HCl to try and bring the pH down.

I was wondering what would keep the pH high?

Any advice would be appreciated.

Cheers,
Scotty

Additionally, The General hardness is about 60ppm and the Carbonate hardness is around 80ppm.

The town water that I use for water changes is bore water with that same hardness tested after sitting for 24hrs.

Maybe try a couple of things.Get another PH test,maybe the one you're using has "gone off".Your GH & KH are very low but there's enough to keep the PH over 7,that could explain the Iron deficiency.
Check to see if there is any dead root accumulation or waste collected somewhere (you can tell by the smell).

What type of system is it? DWC or flood & drain?

If the growbed is gravel or something like that,make sure it's inert.

Is there anything in the system like wood?.I read someone on here had a cane in the grow bed & apparently that was causing the PH to hover over 8,& after removing it,the PH dropped


If it's the API NO3 test I wouldn't trust it.

I forgot to say,if there's an accumulation of some sort of gunk,the Ammonia should rise.Check that too just in case & to rule it out if it's not that.

The pH test does sound like it could be wrong. Definitely cross check it or get a new one and see if you get the same results. There could also be a different buffer system at work, other than the carbonate buffer system. Phosphate buffering is one possibility.

+1 on the last comment from 7341. You want the processes to be aerobic which will bring the pH down.

What's the pH of your top up water? Check it just after you get some and then check the same portion after it sits overnight.

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Once you're certain you are getting accurate pH readings it's probably safe to do the following adjustment.

I usually suggest patience because the biological processes will eventually drive the pH down but if you want to adjust it -
Try adjusting a portion of the system water, say 5 gallons. Keep track of how much acid it takes and once it's pH gets where you want it, let it sit for a couple of hours. Check the pH of the sample again to see if it has drifted and adjust it back to where you want it if needed. Once the pH is stable in the sample you'll know how much acid it takes to adjust 5 gallons of the system water to the correct pH and you can use this to determine how much it will take for the entire system. The ratio of the sample should equal that of the system. Like this -

ml of acid to adjust sample/sample volume = ml of acid to adjust system/system volume

You should already know everything but the ml of acid to adjust the system, which you can calculate.


Adjust the system pH over a period of days by making small 0.4 pH unit changes each day. The small changes help keep the fish from being stressed. Adjust any top up water before adding or it could kick the pH back up.

Hi and thanks for the input so far...



What test do you use? There's not much choice where I'm at unless I eBay it but I try and use local where I can.
I've the API strips and the master test kit that's older but they both agree somewhat on the nitrates.

Same goes for the pH. Both high range and normal pH tests point to high pH in the master test kit along with the strips.


Its flood and drain with very little gravel. Pots filled with expanded clay sunk into 150mm pvc pipe.


There is moving bed bio filter.
Currently reworking the system to put in new swirl filter because original radial flow was too small and not working.
Would an accumulation of solids from fish tank and ending up in the sump and grow tubes contribute to pH refusing to decrease?
The solids filter I've had so far hasn't been able to actually remove any solids, so all of them are in the sump tanks along with sticking to roots poking from the bottom of the pots. I do stir things occasionally to make solids return to the sump. I will, after getting new swirls filter installed, attempt to relocate all solids into the swirl filter. All yellow lidded sump tanks underneath the grow-'tubes' have air-stones.


There is a (I think pleasant) creek smell but nothing smells rank or off. There are no dead spots in the flow of water. One reason why I made the system this way. I didn't want 'no flow' areas in a big grow bed.


The bore town water is about pH 8 after sitting for 12 hours.
I add about 50mL HCl to 100L water and that is added to the system over the course of about 2 or 3 days depending on evaporation and transpiration via a float valve into the sump. Its summer and rather warm in SW WA ATM.

The Nitrates have finally come down (after a week of minimal feeding) to reasonable levels ( 20-40 ppm) and I'm feeding the fish a bit less than recommended to keep nitrates where they are.

I've been adding foliar spray to try and supplement the plants requirements and its helping but I'd much rather have a balanced system.

Maybe I should just be a little more patient and let the bacteria do its thing...The fish are feeding and the plants are still producing a little...

But, the question still stands. What factors make or keep a system pH high?

Cheers!

Anaerobic conditions,big amounts of Alkaline substances,some type of wood (apparently),heat (evaporation),grow bed gravel & top up water.There might be more things but I can't think of anything else right now

If it's extremely hot,the water will evaporate & a lot of Calcium will stay behind (similar when boiling a kettle & limescale is left behind) and that will keep the PH up.


Yes,it's down to a lack of Oxygen (where the accumulation is).Do an Ammonia test, that might also suggest that you are dealing with anaerobic conditions & take measures to help the fish.Surprised the plants are ok with all that stuff on the roots.


NT Labs for Nitrate & API for Ammonia,Nitrite & PH.All are liquid tests.
I have used test strips and I never got an accurate reading,PH from the strips said 6 or below and the API & NT labs both said 7.4


Have you ever measured the PH after that?.Remember to leave it for 24 hours before checking the PH.

What Scotty said might be something too.

Your GH & KH is very low,so it makes me think something else is going on.Especially in aquaponics where the PH is always on the down.It's a struggle to keep it up

You need to get that new swirl going.

In your thread in members systems,your PH was at 7.5 or something.And now it's gone up to the early 8s .Only when you put the pic up I realised it was you.

Back again!,

So the Nitrates are working their way back down...much better figures now Im feeding less. Around 20ppm.

Ammonia checked and 0ppm
Nitrites checked and 0ppm
No wood in the system
Nowhere for anaerobic conditions to exist.
Expanded clay gravel for the grow pots (previously used in system #1)

pH of topup water after sitting 24 hrs is around 6. I did testing to work out how much HCl to use to bring it to around 6 with a given volume of topup water. So I figured that any topup water the system needed (thru the float valve) would be added at pH 6 and would help bring system pH down over the course of the few days it takes for the topup tank to empty.

Fish seem happy enough. They dont hover near the inflow or the surface and they're eating like I feed them once a year.
I havent netted one to look closely, but figure I havent had to yet.


Would you include transpiration with evaporation?
I presumed that the plants would take up the calcium along with the water and not leave it behind.
The evaporation rate would be next to nothing. All tanks have lids and FT has very little airflow over it and covered with shadecloth.

I check both the general hardness and carbonate hardness with strips...should I get titration tests or would the strips be accurate enough?

So apart from keeping the pH of the topup water in check and feeding a little more sensibly, should I just be a little more patient with the bacteria to bring the pH back down? - And in the meantime supplementing the iron and trace with foliar spray...

Once the pH is around mid to early 7's or so I can throw in a little limestone or equivalent assuming the bore townwater doesnt take care of that aspect for me?

Waiting for Uniseals to arrive to put in swirl...

Cheers for the help so far!



Scotty

Wait, you will soon be trying to keep pH up.

When you say a few months, 2 or 3 or 6?

I can't recall exactly, but my pH was high for at least a year or 18 months and since then I constantly have been trying to keep it up.

No,if it were through transpiration,the plants would get chemical burn.That usually happens in indoor systems where humidity is staying very low.Your outdoor system is alright.
If it were to happen through evaporation,you would see dry white "limescale" everywhere and the GH & KH would show huge amounts.


The strips should be ok.But PH,Ammonia & Nitrite I personally wouldn't use strips for those 3,because I don't trust them.

Yes.I use shell grit.

Have you checked the PH of them system again yesterday or today?

In your first post you said been "cycling for a few months",What do you mean?
If it's cycling (like a brand new system) that can push the PH up too.

When starting, it was only a matter of weeks before I was having to adjust both my systems to keep the pH above 6, when using rainwater for top ups, after initially being up around pH8 when cycling. Over the past year when using town water and a bit of bore water, both with a pH above 8 and plenty of Ca, I've not had to do much adjustment to the pH, with it generally around high 6s-7.

I really would not worry about NO3 being at 160ppm, I've often seen over 500ppm in my big system with up to 400 Rainbow Trout, which caused a pretty ferocious rate of pH fall. I've tipped many tens of kilograms of K2CO3, KOH, dolomite, shell grit etc in over the past few years. I've never had to adjust the pH down.

If your nitrates are up in the 100s, put some more plants in, and keep feeding what they will eat, to keep the growth rate up, IMHO.


Oh, forgot to add: If you are off the NO3 scale, just dilute the FT water when testing. 1part FT, 3parts rainwater, and multiply your result by 4.