Backyard Aquaponics
A place to discuss aquaponics

My brother had water at around 8.5 and he added apple cider vinegar to his 1000L tank at a rate of 1/4 - 1/3 of a cup every 3-4 days. After 3 applications his system came good and cleared the pea soup. Might be worth a go perhaps...

hi joel

yeah ive tried some vinegar but it didnt seem to have any lasting effect, maybe i didnt use it for long enough.

i tested my pH again this morning, it was 7.8 (light brown) just like the morning before but the sample i took yesterday morning which i left in the test tube is now 8.8! it actually had gone purple by late in the afternoon yesterday.

can anyone explain why this is happening within a sealed test tube? 7.8 in the morning and then 8.8 in the afternoon. the test tube was under cover outside.

update

day1: put in half tblsp (12g) of sodium bisulphate in morning, tested late afternoon, no change still 8.8 or over. put in one tblsp that night
day 2: tested in morning looked to have gone to 7.8 but then the sample changed and went dark purple. tested in afternoon and pH was 8.8 or over. added 2 tblsps (48g)
day 3: morning test-pH 7.8 added 2 tblsps of sodium bisulphate (48g). i did not do this yesterday after a similar pH reading in the morning so i will see if this makes any difference to the afternoon reading

Interesting. If it is due to biological activity you could confirm it by boiling some water. Put some boiled water in one test tube, unboiled in another, see what happens to ph over a day or so. I'm not sure how this will help, but it would be informative.

Another curious factor is that ph usually drops at night if it is caused by biological activity (CO2 increases acidity). Any thoughts, people?

DOH! I miss-read and thought you had it setting overnight, not during the day! Try overnight as well and see if ph drops. That would be a good indicator of a biological factor.

finally got the pH to 7.2

yesterday morning pH was 7.8 and i then added 2 tablspns of sodium bisulphate. at lunch time yesterday there was no change. so i added 3 tablespns to see if i could get down to low sevens.

this morning read 7.2 with no fish deaths yet so thats good. ive also gotten some big water lillies to shade the water surface, i know that these will compete with vegies for nutrients but im hoping to get some extra fish to account for this.

the water is starting to look a bit clearer, i can maybe see 10-15cm into the water

hi clay,

when you said you were changing your water.. do you use tank water??

the reason i ask is that my tank leaches ?lime .. my water has a ph of about 10. apparently this is not bad for ppl bout a bitch to grow plants with.. not sure how fish will go in it..



hope it works out ok... great system btw....

hey

im using tap water at the moment for top ups unfortunately. with the sodium bisulphate ive got my pH down to around 7.2 and im shading my tank with a beach umbrella

ive also added more fish, about 15 more goldfish to the system. plants are looking a lot better, tomatoes are starting to grow now.

one thing i did notice was that my pH was different if i measured from the surface of the water than if i got a measurement from in the middle. not sure why this is.

Is ph of deeper samples lower? Sometimes lack of circulation can cause lower O2 and higher CO2 deeper in the water than at top where gas exchange takes place.....or so I've read.

I would find this totally strange and un-explainable in a recirculating tank environment...

out of couriosity of a newbie...

would the lack of circulation be a cause of your increased acidity?? as the co2 and h2o combine to make carbolic acid.. (hi school chemistry was a reallllllllllllly looooooong tima ago!!) and i would guess that as carbolic acid breaks up easy.. the circulation of water would as, hydrophilia said, break up the acid into co2 and water..(tim flannery would be choking on his tofu burger about now.... ) realeasing co2 back into the air???


maybe??

ooops,,

it's not acidic......

too alkaline.... way too many conversations going on in my head!!!

sorry please ignore my last post!!!!

Clay, water pH changes over time as metals within the water oxidise (I think that is the reaction- it has been a while since I had to do water chemistry every day ), this would have been exacerbated by the water in the vial heating up during the day. pH readings must be taken immediately upon collection.

To maintain metal levels for analysis, water samples being sent to a lab should be refrigerated. While working at Mt Lyell I use to send about 200 water samples off a week for analysis and we had to put them on ice to get them to Hobart or up the North Coast to a lab. It was a such a pain (and expensive) we ended up seeking NATA accreditation for our own lab on site. When I was FIFO it was always a big disappointment to everyone else on the plane when they would realise the esky I was carrying back to Perth was full of groundwater samples and not cold beer

pH, TDS and EC was always measured in the field at the time of collection using calibrated portable meters.

It is amazing how much knowledge you forget, I lay in bed last night thinking about this more. Sulphidic rock oxidises when exposed to oxygen and water to produce sulphuric acid and as your sample has gone the other way (basic) there has probably been an opposite reaction - reduction equation. What suburb are you in, any idea about the pipes and local water source? Could be high carbonate content? Is there a chemist here that can refresh my memory?

Either way I doubt that a pH of 8 comming out of your drinking water taps meets ANZEC water quality guidelines (1996) I can't find a copy online and I no longer have a hard copy but you may have a copy somewhere at work to check? Just make sure you are looking at the drinking water section and not the stock water section.