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PostPosted: May 11th, '20, 11:11 
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Purpledino wrote:
Hi guys, is it normal to have to buffer the system weekly as pH drops to 6.0? Or is it something to do with water hardness?

It suggests the carbonate level in the water is low. You need to both buffer (add carbonates) and raise the pH back up. The easiest way would be small additions of Dolomite Lime (Calcium Magnesium carbonate) and Potassium bicarbonate in a ratio somewhere between about 3:1 or 4:1 by volume. That will both raise and buffer the pH, but will hopefully also keep the Ca, Mg & K in a decent ratio with each other.

I would aim for a pH up around 6.7-6.8, but get there in small increments of about 0.3 or 0.4 per day.

Also, it is common, once the natural pH decline has occurred and the pH in a system has dropped into the 6's, to be adding pH raising and buffering agents weekly. The frequency with which it is required is determined by the amount of Nitrification taking place in the system. The more fish, the Nitrification, the more often it will be required.

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PostPosted: May 11th, '20, 12:32 
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Thanks for taking the time to share such valuable info.

How would you proceed if your crops are showing signs of both K and Fe deficiencies please?

There are lots of information regarding this topic and I wasnt able to find anything concrete. Much appreciated. I will follow your advice.

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PostPosted: May 11th, '20, 14:15 
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Purpledino wrote:
How would you proceed if your crops are showing signs of both K and Fe deficiencies please?

If you definitely think you have a Potassium deficiency issue, kill two birds with one stone... Raise and buffer the pH, as well as fix the deficiency, by adding a little Potassium bicarb. I'd suggest somewhere in the region of 1x level teaspoon per 500L of water as a starting point. Then revert back to the Dolomite:Pot bicarb ratio mentioned before for, to keep the carbonates and pH in check in the future. I'd also suggest using proper measuring spoons when doing this sort of stuff.

As far as Iron is concerned, you don't need to add anywhere near the levels recommended on many Youtube vids etc. The single IBC display system in my shop gets literally a pinch of EDDHA Iron into it's 500L of water every 4-6 weeks and the plants do just fine. After I've finished bagging up the EDDHA iron for sale, I'll sweep any spilled Iron off the bench top with my hands and brush it off into the system, it's literally the equivalent of a decent pinch. Iron is very easy to diagnose early and just as easy to rectify, with any Chlorosis reversing within just days of adding EDDHA Iron.

In saying that, you need to ensure you definitely have a particular deficiency before taking actions to rectify it, because you may actually make it worse, or cause new issues, if you are taking the wrong action. As I said in my initial post, I don't think you plants were showing symptoms of either Iron or Potassium deficiency.

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PostPosted: May 11th, '20, 14:50 
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Yes I'm sorry. I meant to say Mg deficiency. Is it recommended to add 1tbsp/1000L weekly?
I'm also thinking 1 cap of Seasol monthly

I am surprised to read about your experience with Fe. Indeed, the majority of info out there definitely advise for more than a pinch.

It's interesting to see that my nft is not recovering from the buffering unlike my raft bed and media bed. Water flows in my systems as follows: FT > RFF > Small particles filter > ST, then in series to Raft bed >Media bed > NFT
So I've changed my buffering by pouring equal part of the mixture at the inlet of my raft, media bed and an aquarium sponge at the inlet of the NFT.

Plants are doing much better after following your suggestions [THUMBS UP SIGN]

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PostPosted: May 11th, '20, 20:54 
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Looking at your pics,there's nothing wrong with the plants.

What Mr Damage said is all correct but that's for those who are experienced with the water chemistry in aquaponics.You might cause nutrient lock out doing that if you mess up (Calcium).
I suggest you crush up shell grit (Calcium carbonate) & leave that in the system to bring the PH up & foliar spray epsom salt (Magnesium) and Potassium bicarbonate so you don't cause a lock out.

Calcium is the most common deficiency I've come across,adding K & Mag to the root zone might cause at least one of those 3 to be locked out if not done correctly.

But only add things if you know there is a deficiency.

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PostPosted: May 11th, '20, 21:46 
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Thanks for your input. I had read that Ca was the last mineral we had to worry about as it would be found in our water. So that is the mineral I buffered with the least. My understanding is to buffer with all nutrients to prevent competition to raise pH, but respecting certain ratios of which Ca was the least. [scratching my head]

May I know your dosage for K & Mgfoliar spray? I've tried adding K thrice before and it caused leaf burn, so I stayed away from it in my foliar sprays [CONFOUNDED FACE]
For Mg in foliar spray, I use 1tsp for 1.5L. Does that sound right to you please?



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PostPosted: May 11th, '20, 23:40 
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Sorry,I should have been more specific.I put pure water in the system 0ppm,that's why Calcium was my most common deficiency.

You're wanting to buffer/raise the PH up,not supplement Calcium.Water in nature will be buffered mostly by Calcium (rivers & lakes),so it would be best to mimic that,you already are by putting the tap water in.You can't keep buffering the water with Magnesium only because you're going to be putting tap water in all the time as well (causing at least 1 lockout).That's why it's best to only add one of those to the water/root zone to prevent anything going wrong & since you're using tap water (straight from the tap with no RO filtering) it's best to stick to Calcium.Hope that makes sense.

Purpledino wrote:
May I know your dosage for K & Mgfoliar spray?

Depends what you're using.Dolomite can't be foliar sprayed,but if it's epsom salt,read the instructions on the box.On mine it says "20 grammes per litre & apply to foliage at monthly intervals" (epsom salt).
And Potassium bicarbonate = 1 table spoon to 5 litres of water.Do it only if you know there is a K deficiency or toxicity problems will start,as you have found out.
Both are for foliar spraying.

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PostPosted: May 13th, '20, 17:17 
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Thanks for your clarification.

Its interesting to me that you experienced aquaponic practitioners correct a deficiency only when it appears. What if you're selling the crops though?

That differs from what I was told by an aquaponics teacher :/ He advises to buffer with supplements biweekly, and once monthly with Fe before any deficiency shows up as a maintenance measure. Suggesting to do so in a ratio where Mg is the most, then K, and small amount of Ca. He runs 2x 900L FTs, 3 media beds, 1 large raft, 1 nft, and a dinky filter; and his system and crops look like a picture perfect oasis. Not to mention high fish densities whereby the fish are in like sardine boxes. I'm dumbfounded haha

Perhaps it boils down to the fact that my barrel system and 200L FT is supposed to experience abrupt fluctuations unlike larger 900L FT systems which apparently are more stable? Instead of guessing the deficiencies at times, perhaps it's worth investing in testing equipment for the aquaponics lacking nutrients if it fits one's budget?

At this point, perhaps it would be cautious for me to make a foliar spray of K,Mg and Fe mixed with some Seasol?

I'm going to try till I succeed [SMILING FACE WITH OPEN MOUTH AND SMILING EYES]ImageImageImageImage

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PostPosted: May 14th, '20, 02:06 
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Purpledino wrote:
correct a deficiency only when it appears

Some on here must supplement,especially when it's a 10000L system.So if you need to supplement with a system that big,it's best to do it in small amounts all the time & not just dump it in all in at once.Those that have massive systems have a lot of experience,so they know what plant is going to deplete certain nutrients and how much to add,without it taking a toll on the Ph & other nutrients.
With your system it's not an issue unless you're over doing it,like trying to grow 100 tomato plants.Iron shouldn't be an issue in yours,it would only be PH related.Iron is a micro nutrient.You have been adding Potassium,Mag & Calcium in big quantities too often,mostly to bring up the PH.You really can't fight the PH.And now it's causing lockouts.

Try using crushed up shell grit,figure out much how is needed in your system to hold the PH at 6.8,then just wait for it to run down (about 2 months depending on temp & stocking density) & then when the PH reads 6.2 or 3,replace it,unless you have fish that needs specific PH values.Then when you see a K deficiency,foliar spay the plant so it doesn't mess with the water chemistry.

Purpledino wrote:
his system and crops look like a picture perfect oasis. Not to mention high fish densities whereby the fish are in like sardine boxes

The Nitrate is reading off the chart.Plants love it!,when you see nice big very green plants,they have had a huge dose of Nitrogen or in aquaponics,large amount of Nitrate.Too much Nitrate can cause nutrient lock outs too.

Try the foliar spray & let us know whats happens please.

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PostPosted: May 14th, '20, 14:59 
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Ok thanks for your input. Lots of school of thoughts when it comes to Aquaponics. I suppose that every system is different.

I am having trouble getting my hands on some shell grit. Anything I could do with egg shells?

Its interesting to me how some plants may do well while others show deficiency(ies). Still lots to learn on my part.

I will try to work things out with foliar spray since I may have messed up my water chemistry.

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PostPosted: May 17th, '20, 20:46 
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Purpledino wrote:
I am having trouble getting my hands on some shell grit. Anything I could do with egg shells?

Yes,it would work the same way but you are going to need a lot of it.
Purpledino wrote:
Its interesting to me how some plants may do well while others show deficiency(ies). Still lots to learn

The plant world is a universe.So much is going on it's unbelievable.

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PostPosted: May 17th, '20, 21:30 
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Thanks
First bunch kangkong harvest for padthai tonight Image

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PostPosted: May 18th, '20, 03:10 
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Purpledino wrote:
I am having trouble getting my hands on some shell grit.


Crushed coral will also work - https://www.amazon.com/s?k=crushed+coral&ref=nb_sb_noss_2

Please remember to add it in such a way that you can remove it if the pH climbs too much. I use a mesh for this.


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PostPosted: May 25th, '20, 13:37 
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Hey guys, thanks to you. The crops seem to be doing better.

Could anyone give me advice on how I can prevent crops like choy sum and bok choy from bolting please?

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PostPosted: May 25th, '20, 13:39 
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Some fresh baby bokchoysImageImage

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