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GH / KH / Carbonates / Bicarbonates trying to make sense of it all.

My system has been running for about 7 months now, it's about 1300 L, / 350 G total with about 60 fish a combination of tilapia and gold fish all between 3" & 6" in size. I'm using one IBC 12" deep filled with broken clay brick as the media, and a second IBC 14" deep with a raft on it. Lots of air stones in different locations throughout and the media bed is constantly flooded.

The system is in my basement and each IBC is under a 400W MH lamp that we run 12hrs + per day.

The issue - my top up water is a PH of 7.2 - my system PH will  sit at 7.2 when I don't adjust the PH of the top up water via HCL. Some plants have some brownish spots on them - chard, bok choy. and the chard leaves don't always flatten out / open up, they often stay curled under. This issue seems worse on parts of the raft but does appear to some degree everywhere.

I was thinking (dangerous at the best of times but usually just to myself and my wallet) that based on what I had read maybe it was a calcium issue. I picked up some test strips, and my GH (General Hardness) is off the chart so above 180 but my KH (Carbonate Hardness) is below 40 - again, this is based on some test strips (from what I have read test strips are suspect at the best of times)

In the name of full disclosure, I have added some chelated Iron, some KCL and Mg via epsom salt.

I am greatful for any insight you can provide

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I had a water analysis done at a local lab

Bicarbonate 41.7 ug/ml ( I think that is the same as PPM)

Carbonate came back as BDL ( below detectable levels ) and the lab indicates the can detect down to 10 ug/ml.

So maybe this is really strange, but my lettuce seems to be doing pretty good but I'm trying to understand if anything is way off?? I have read that we should be shooting for a KH of 40 minimum but is that the same as this Carbonate reading?

I will attach the full analysis.

Thanks for any feedback you can provide.

Attachments:

Hi Bart. People on the forum seem to use the terms 'carbonate' and bicarbonate' interchangeably, but in reality in any fresh water eco-system it is bicarbonates that are providing kH, alkalinity, buffering capacity, an inorganic carbon food source for the bacteria, and all that other good stuff. It is only when you get into saltwater systems that carbonates start to play a role. So don't worry one bit that your carbonate reading came back undetectable.

Nothing really seems out of whack...calcium is perhaps a tad high, but there's not much you can do about that except maybe add just a bit more potassium.

You can sow down with the iron a bit if you want (not because your near any "dangerous" levels or anything...your smack dab in the middle of the high end of the 'generally recommended' level of 2 to 3ppm (which I believe to to a pretty high number that comes from the hydro world and is a general recommendation meant to cover most ALL plants at ALL stages of growth...hardly necessary for lettuce, chards, greens etc...Again, no harm in it, just a waste of iron chelate and money).

Could you post some pics of the curling and brown spots? There are many reasons and therefor ways in which a leaf will curl...Is it length-wise down the middle like a taco, or is the tip curling toward the base? Are thy curling upwards, or downwards...the answers to these 'descriptors' will indicate whether the curling is due to simple physiological stress, a virus, a nutrient deficiency etc...

Hey Vlad, thanks for the feedback. Most of the leaf curling issues have resolved themselves - I had some alge issues I've been working on and the fish are starting to eat a little more may have been a phosphorous issue. I realize now the brown spots were from some spider mite so i've been yanking the shitty plants using a light soap spray on some of the others - making progress it's all good.

Very cool Bart (except for the spider mites...man, I friggin hate those bastards)...

how much did you have to pay for the water test?  A local lab quoted me at $500 for a test.

Bart said:

I had a water analysis done at a local lab

Bicarbonate 41.7 ug/ml ( I think that is the same as PPM)

Carbonate came back as BDL ( below detectable levels ) and the lab indicates the can detect down to 10 ug/ml.

So maybe this is really strange, but my lettuce seems to be doing pretty good but I'm trying to understand if anything is way off?? I have read that we should be shooting for a KH of 40 minimum but is that the same as this Carbonate reading?

I will attach the full analysis.

Thanks for any feedback you can provide.

Wow that's a little rich. The test cost me $34

The company does testing for agricultural purposes, I think they called it an irrigation water test. Details are in the PDF attachment above.

Good luck finding a better provider.

$34 seems like one heck of a deal.  I bought a bunch of test kits but gave up testing after there was over 8 tests.  I spent like $200 on tests for Ammonia, Nitrite, Nitrate, Phosphorus, potassium, iron, magneseum, caceum, general harness, carbonate hardness.  Its hard making sense of all the numbers.   I started adding Glacial Rock Dust instead of Calcium, bicarbonate.  Magnesium, potassium, carbonate, and iron.  The rock dust had everything i had been adding, and makes thing a lot simpler.  As a added benefit i notice the the rock dust worked very well as a buffer.         

Thanks for the response Bart and Jonathan.

A quick google search for water testing in the US doesn't look very promising.  This site - http://www.budgetwater.com/mailed_tests.htm comes up and their prices start at $135 for pretty much what I can test with a pond test kit.

Anyone know any test labs in the united states where we can get a comprehensive water test for under $100 ?

These guys look like the might be able to help http://www.texasplantandsoillab.com/water-testing.asp
Looked like the standard test was $53 and includes the basics, $70 for the next test up the list.
Good luck.

Thanks for the tip.  I found a lab called soilkits.com that charged $160 for their most complete water test.  Since this is my first test, I wanted to try to cover more area's as I'm not getting great results from crops in my system.

First, my PH is 6.6.  For some reason the sample tested lower.  I suspect this is from the sample being shipped and taking nearly a week before it was tested.  I have several PH meters and use a chem test kit routinely to verify.  

I'm running RO water and I've added maxcrop with cheleated iron on a few occasions.  The system is about 3 months old and I've been using what I believe is good quality pellet food.  Fish are ok but I did lose 1 larger fish a month ago.  Tomato's and lettuce are ok but some plants are not doing as well and show some signs of deficiency.

Phosphates look high at 6.13

Chlorides also look high at 131

Alkalinity is very low 4.70 which I had confirmed with my own tests.

Hardness is too high at 274 which I had also confirmed with my own tests but not nearly as accurately.

All of my metals seem to be low (iron, zinc, boron, copper, manganese)

Can anyone else comment on this or make suggestions?

Fred here is a resource that can help sort out what levels are optimum. I don't shoot for optimum but it helps to know when you are way off the mark or over.
http://www.scribd.com/doc/116298550/Hydroponics-A-Practical-Guide
Cheers

Thanks for the great link !

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