Backyard Aquaponics
A place to discuss aquaponics

with my system ticking along well (sort of)
Nitrates 0
Nitrites 0
Amm 0
PH 8.2

how the hell do I get it down, and why is it up so high.

There is no limestone in system

pics show lack of healthy plants although strawberries trying to grow I must be doing something right.

your advice please

Water source?

Give it time and you will be trying to buffer it up :-)

its all rain water from poly tanks. comes out of tank PH 6.2

oh dang I wish and dream for buffering it up.

Looks like a potassium deficiency... or maybe multiple deficiencies.
What are the characteristics of the system (size, number of fishes, what food & how much) ? how long has it been running ?

I know exactly how frustrating this is Tonnz. I had the same crap happening in my system for the first two years too, except I use well water. Of course, I should go do some water quality tests on my own system before I suggest anything. I just wanted to commiserate with you. I finally removed the strawberries from the towers I was so proud of in the beginning. They are doing a little better in the dirt, but I still have a lot to learn about water chemistry and plant biology
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I keep thinking about this and hoping by having aquariums too I'll eventually figure something out with this pH, KH, oxygen and CO2 stuff, so I looked at it again from an aquarium perspective here is an article about CO2 injection and how it relates to KH and pH - https://www.practicalfishkeeping.co.uk/features/articles/co2-striking-the-balance
Brian

Looks like a potassium deficiency... or maybe multiple deficiencies. if this is possible what do I treat with that wont cause fish to go mental.

Thanks Brian thats a read for lunch break.

HI Tonzz, Potassium Sulphate (sulfate of potash) may help, alternatively Potassium bicarb, bunnings will have as Eco-Fungicide, garden shops may have is as eco-rose. Pot bicarb may not help with your high pH tho as it may buffer it at this level.

With high pH you may also be getting iron or other nutrient lockout, try foliar applications?

Have you done an acid test (vinegar, dilute pool acid or the likes) on a jar/bucket full of your substrate? might have some limestone in there in small amounts as a contaminant?

have you added any other limes/hydroxides?

the gravel is ALL clear... you get strange looks at the quarry/ landscape suppliers when you rock up with a number of jars and bottle of white vinegar, mind 3 of the staff have now looked over my system and impressed.

what if I sprinkled dolomite lime powder this reduces acidity...or have I got it round the wrong way.

Try some of your gravel in your rain water for a day or two and see if the ph shifts .

I set up a system for a friend and we did the vinegar test on some options and settled on this nice slate looking gravel that didn't bubble with vinegar , a week later ph was really high in the end we switched to scoria.

That quartz looking gravel does have seams in it .

The high Ph has to be coming from somewhere , either gravel / top up water / or a nitrite spike (I found that one out the hard way)

Fish food is formulated for fish not plants so typically its very low on Calcium / potassium / and Iron so these are the most likely deficiencies we come across .

Your ph is high so calcium deficiency is unlikely , best to foliar spray Iron weekly , Potassium Sulphate would be the easiest obvious option as it wont raise your ph like "Carbonates " will .

Dolomite with RAISE your ph as its ground limestone magnesium carbonate

Im coming to the conclusion that that strawberries are not worth the effort in aquaponics I grew some terrific strawberries at my previous property (Wanilla) but only the one year they are pretty fussy , too hot , too cold , too windy list goes on . The grow bed space is better used for something else .

Don't wish for buffering up too soon its a real pain , I am going to get a digital ph and temp meter so I can just read off the shift as I walk in then I will be able to work out over time how much daily to add to keep it more or less stable instead of delayed swings of varying degrees

The pH should come down on it's own unless it's being shifted up by something in the water or the media. I wouldn't think this would matter since it's been sitting in rainwater tanks but try taking some of your top up water and just let it stand for a day before testing it to see if the pH is higher than when you first took it out.

For lowering the pH hydrochloric acid (aka muriatic acid) does well but you need to be careful with it and follow the instructions for handling. Take a sample of your system water in a bucket (5 gallon buckets or equivalent in metric should work). Adjust the pH of the water in the bucket to around where you want the pH to be (probably 6.2 to 6.. Keep track of how many mls of HCl you use. Let the sample stand for a few hours in case the pH drifts and you have to adjust it again - repeat as many times as needed. When you're done you'll know how many mls it took to adjust the sample and the ratio of the mls of HCl used for Z Liters of water in the sample should be the same as the mls needed for Y liters in the system. You wind up with this formula

mls needed = Y liters in system x ( mls of HCl used for sample/Z liters in sample)

Once you know how much it's going to take you can adjust the pH over a period of days by adding small amounts so that the pH doesn't change more than 0.4 pH points at a time. This helps the fish adjust without as much stress of shock.

Keep in mind -
1. The API kit can't read below pH 6.0 so a reading of 6.0 means the pH could actually be lower and you need to bring the pH up.

2. If you have algae in your system they can cause large pH fluctuations, especially if the carbonate hardness is low. The high pH readings you're getting might be much lower at other times of the day so test at a few other times before you go whole hog and try to make this adjustment.

Once the pH has fallen and you're having to adjust it back up you'll need something like a mesh bag with some form of calcium carbonate (oyster shells, crushed coral, limestone...) to buffer the system up. Put the bag in the system when it needs to be buffered up and remove it before the pH climbs too high. Occasionally you may need to use something more drastic like potassium bicarbonate, potassium carbonate, Potassium hydroxide or calcium hydroxide to bring the pH up - you can use the bucket method to help figure how much to add but some of these are caustic and won't take much so use caution.

You can always wait if you don't want to mess with any of this

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For the deficiency, I would spray apply potassium bicarbonate or potassium sulfate. A good starting point that I've used is 1 tablespoon per gallon - it may take more than one application but allow time for the plants to green up before hitting them again.

Looks like you must be applying iron because you get iron lockout at this pH and the new growth would have interveinal chlorosis if you weren't (like what you see with the old growth in your pictures).

it was crappy cold today and as Iam off in a weeks time to visit my fit 99 year old dad in NZ thought I would keep warm inside. so a lot of reading then shopping for hydrochloric acid, Potassium Sulphate & Iron chelates see what they do over the next few weeks.

Otherwise the system may completely change over to wicking beds etc.I hope not the $$$ invested already.

Tonzz just visit the local bunnings: Hydrochloric acid (pool acid), Sulfate of potash (fertilizer) and Iron Chelate (also in the garden section), should cost you all up around $30 dependent on acid volume you buy. The Bondall brand indicates to use ~2.5mL/1000L to reduce pH by 0.1 point so 1L of acid will last a fair amount of time

sorry Graf, just re read my last post ....I meant I purchased those today, interesting to see what happens over next few days.