Backyard Aquaponics
A place to discuss aquaponics

Greetings!

My system:

*About 40 gallons in a chop and flip system
*Mother Earth Hydroton as my grow media
*I think about 10-12 goldfish
*I test with API kit
*water from my well, which is quite hard, but good otherwise
*initial pH of ~7.0 after adding water

So, I initially cycled my system (fishless) about 5 months ago. I eventually got good nitrate numbers (~80 ppm), with no nitrites or ammonia, and so added fish and plants. My pH was high (and I didn't do an initial test when I started my system) - about 8.4 - but I figured that'd go down as the system matured and continued to produce bacteria.

I tried pH Down (also from API, I think), water changes, adding store-bought water, and the pH would always go back to ~8.4.

I recently became suspicious of my media, and think I didn't rinse it well enough - even though I know it's supposed to be inert. So, I completely took my system apart, I'm currently soaking the Hydroton in a slightly acidic solution (with vinegar), cleaned it (not with cleaners, and not completely), and reassembled.

I'm now trying to cycle again (yes, with fish, because that's where I'm at), and so last night I added water (from the well), put the fish back in - with no media! - and tested the pH. After about an hour, the pH was right at 7.0. However, this morning it's back up at 8.2-ish.

Is there something about sitting for a while that makes a higher pH materialize? It's so confusing to me, and as a civil engineer I've even taken classes in water chemistry, lol!

I'm currently resolved to let the system mature, then add the clay back in (or maybe just add it in after I'm convinced it's rinsed well), and then hoping the pH stabilizes. I've researched so much, and just haven't seen a situation quite like mine.

Any thoughts would be greatly appreciated, and while anecdotes are great :-) what would be most helpful is principals that I can keep in my back pocket and apply. Thanks so much in advance!

The Carbonate hardness is high (KH).
It's the buffer that holds the PH in place.You put some acid in now,bring the PH to 7 & then in a few hours it'll jump back up to 8.The water you're putting in,keeps adding Carbonates to the system.

Put the system back together again (fully),and over the next couple of weeks add pure /(ish) water to the system,distilled,de-ionised or rain water & that will use up the buffer that's holding the PH in place.Then it'll gradually go down.

Is there any wood in the system?

Thanks for your reply!

No wood in my system. Right now, I don't even have the Hydroton in there; just my 55-gal pickel barrel, my pump and piping, and my fish.

I understand that my hard water is keeping the KH high, but shouldn't that just control how much it takes for the pH to swing? I.e. If my water tests at 7.0 out of the tap, shouldn't it hold there instead of go to 8.4?

I don't have a rainwater collection system in place, although I could just catch it in a barrel for the small amount I need, or even buy some cheap distilled water from Walmart if necessary.

Water straight out of the tap will show 7 being under pressure,after 24 hours & mixing with the air it'll show it's true PH value.Mine comes out of the tap at 7 but after a few hours it shows anywhere from 8-8.5.

And yes after it shows its true PH value the KH will hold it there.

Buying distilled water is a good option because you'll only need a few bottles but once KH weakens down & the PH starts dropping,you'll be fighting to keep it up

Another option could be acid,a lot on here use that.Add the acid to your top up water & bring the PH down to 7 or 6.5,then add it to the grow bed.

Very helpful - thanks, again.

Any good resources/links/etc. for acid? I've used pH down from my local pet store, but it took too much to reduce the pH enough, and so I'd want something in bulk (but also not too expensive).

I could always add a mixture of distilled water and well water, no? And just get it down to where I know what the pH will be based on ratio?

Hiya ncpfist, welcome to the forum.
Don’t use pH down if you’re eating the fish. Muriatic acid is cheaper and beneficial for the fish. Treat the top up water and once off gassed and treated it would be cheaper than buying water from the shops. Rain water collected from a tin roof should not be used.
I’m curious why 7341 asked about wood, please explain?

In any case the pH will drop once the fish get bigger and eat more.

Then you will be fighting to keep the pH up :-)

I don't know where you could get things like that over your end,but acid like Muriatic HCL is cheap & easily available.You won't need to buy much.

Just put the distilled water into the grow bed while it's flooded at 1 Litre/0.21 gallons at a time & that will eat away at the buffer.Remember not to swing the PH too fast,all this must be done over a week or 2.

Some had canes for the plants in the system & for some reason that was pushing up the PH,I've seen that a few times.

Thank you so much, everyone. Having a variety of perspectives forms a nice amalgamation of knowledge, and is very helpful.

I have goldfish, so not eating them.

Just any old muriatic acid, or should it be food-grade (if there is such a thing) since we will be eating the veggies?

And the more I think about it, the more I do see the wisdom in gradually letting my system mature; rather than fighting the pH to get it down, only to have to fight to get it back up.

Anything special to do while I don't have plants in, or should the biological process combined with adding top-off water as-needed be enough?

Lot's of good advice here so far. I caution you to look past the labels like "pH down" and see what the product actually is. Most aquarium pH down is sulfuric acid, as mentioned above muriatic acid is hydrochloric acid. These are very strong acids that should be handled and stored with extreme care.

We all have our own preferences, and I avoid sulfuric and hydrochloric acids in favor of phosphoric acid. It is readily available in a hydroponics product called pH Down, is food safe (they add it to soda and lots of other stuff), and it brings phosphorous into the system which can benefit fruiting plants like tomatoes.

That said, I rarely add acid. I've had a gallon of pH down for several years and it is still half full.

Many people run their systems at higher pH and they work very well. Some nutrient lockout may become a problem, but I don't recommend chasing numbers for the sake of the numbers.

Instead, get your system cycled and stable, and address issues with the plants and nutrients as they arise. One preventive action I will recommend is having some salt in your system. 1 - 2 ppt is a good range to help protect your fish from freshwater pathogens. If this is new advice, the correct types of salt have no additives of any kind and 1kg of salt per 1000l of water = 1 ppt.

I have tinkered with acid to dropping PH. While doable, it never goes as planned. There is so much more to PH thats hard for me to understand (basicly you a general hardness and carbonate) . The acid just eats away the carbonate buffer and you are left with wildly swing General Hardness (general hardness is where i start getting lost and how it interacts with acidic components of the water). My lack.of understsnding is what i get for reading college level published papers with a back woods southern public education. I prefer to not use hydroxides to raise my PH as i want that buffer.

To give you an idea, with no carbonate buffer your tank ph can swing over a point just by the sun going down. Thats bad for fish. When the suns out your tank algae is making oxygen and pulling co2 (co2 is an acid) out of the water and giving it oxygen. Thats a good thing high oxygen levels and PH increaseing battling the fishes CO2. Sun goes down and plants dont photosynthesis, they start using oxygen and making small amounts CO2 for energy. Now you are rapidly acidiphying your tank. It gets even more complicated than that because it depends on water chemistry and host of other things. That was just an overly simple example of what can happen. Your tank oxygen transpiration is only enough to keep your fish alive but they are now double stressed st night from the sudden PH shift and low oxygen level.

Its best to just wait it out. It will come down. Just foliar feed while its high with some seaweed extract with a bit of iron. Most of those supliments have foliar feeding directions so you dont burn leaves. Switch to a high iron chelate helps also but its expensive though it last for years.

No need to wait for plants i always add them first while its cycling. I dont really worry about PH unless its over 7.5. I actually like my PH at between 6.5 and 7.

I also have hard water here. My tap water has a PH of 8 to 8.5

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My suggestion for muriatic acid, hydrochloric here in Aus, Is because it was Mr Damage’s recommendation;

Quote;
“use of Phosphoric acid can promote algal growth.

Hydrochloric acid (Muriatic) is a better option. It's cheaper, generally easier to access, and once in the system it dissociates into Hydrogen (water) and Chloride. The Chloride is beneficial for fish health, assisting in developing and maintaining their protective slime coat.”

Yes, acids are dangerous and care needs to be taken when handling.

Ncpfist, get your plants in now mate, you can add seaweed emulsion to help them, it contains no ammonia and doesn’t affect the pH.

7341, thanks, do you mean canes used for stakes? I have driftwood collected from the beach in a tank in my system and I can’t remember why…

Sorry for the late reply.
Yes.Some canes were causing it too.There is a post on here a couple of years ago where the cane was causing the PH to stay high.But some other members have canes in their systems & seem to get away with it

The driftwood you have obviously isn't causing any problems but who could really know what type of wood it actually is.If you ever find out,do let us know.

I've used muriatic acid last spring. My fairly new setup was something like 8. I used because I already had some. I mixed no more than a couple drops into 2 gal. of tap water then directly into my tank with no adverse effects. Shortly after that I was at the local aquatropics store where he told me he'd be scared to death to used muriatic acid. Then proceeded to sell some ph down to me naturally. I haven't used since. But I probably will in the future. "Sparingly" is key as others have pointed out. 1 drop will burn a hole in your clothes, skin, lungs if you breath it. It is commonly used to etch concrete and even glass. I've quite alot of experience with it outside of aquaponics.