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lagreca

pH balancing new water

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I read in a book "It is important that any water used for refills or new batches of nutrient be pH balanced to +/- 6.0 (depending on crop) before mixing with your concentrated nutrient powders or liquids."

Is it true you should pH balance the water for the nutrient tank before adding nutrients?

Problem:

I added new RO water (pH 7.07 @ 86 ppm) to my nutrient tank last night. Then I stirred in my 3 tablespoons + 1 teaspoon nutrients (Flora Nova Grow) and the pH dropped to 5.2. I was worried this was too low for my plants, so I added 2 gallons of RO water which brought the tank to pH 5.38. 12 hours later I checked and the pH was 6.10. Why the large swing in pH overnight? How can I prevent this?

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What you read was true in most cases. Hydroponic water needs to be pH buffered prior to adding nutrients or there is a possible risk that the nutrients could settle on the bottom of the tank and hence not available to the plants. When buffering try to use acids/alkaline chemicals as they don’t react with the nutrients where as natural substances such as shell grit react with the nutrient causing various chemical reactions producing other compounds that commonly precipitate out becoming non available to the plants. Additionally, this may also adjust pH levels overnight.

Generally electronic pH meters are fairly accurate if calibrated properly and left in the sample long enough to stabilise say 3+ min, however, other water based test kits can vary enough to give a false result so it may be a incorrect reading. Also make sure that the solution was fully mixed and well agitated to get a uniform pH and then take the reading.

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Hi,

Generally electronic pH meters are fairly accurate if calibrated properly and left in the sample long enough to stabilise say 3+ min......

And they can be hopelessly inaccurate, too. I have a Milwaukee meter and it never gives the same reading twice in row. I much prefer the freshwater test kits that use the liquid drops.

I agree with Jonathon's observations about buffering. If you don't sort the pH before you add the hydro nutrients, you run the risk of locking up some of the elements in the nutrient mix.

Gary

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G'day :)

I also run a hydro system and through trial and error and by asking many questions (about ph and cycling to both Gary, Jonathon and Lyn from Boxsell hydroponics) thought my experiences might help you a little.

I decided a while ago (due to a substantial delay in getting my sleepy cods) to go the hydro way rather than aquaponics and put the fish in my dam - although I still use aquaponic setups. In my situation, I have bore water that is plentiful, but limited rain water. The bore water is very hard and has a cf reading of 2.50 (about 1300 to 1700 ppm) - which is high (tomatoes usually need a CF level of 2 to 2.2). It takes a lot of acid to reduce the ph. I have heard that nitric acid is very good for hard water, but is extremely difficult to get a hold of. Hydrochloric acid does not work well with my water and requires a large amount to lower the ph. Lemon and Vinegar are too weak for my purposes.

I am presently using phosphoric acid with decent results. Before using the bore water with my system, I control the ph first. I have a 900L tank that I fill up with bore water. I add acid every 2nd or 3rd day and test with normal ph drops - I haven't found ph metres that great...although EC metres are very handy. It takes about 10 to 14 days for the ph to stabilise, but once it does it is fine for about 3 weeks...which is about the amount of time that I need before swapping the water and putting in new nutrients. When initially putting in the acid, the water will go a little milky, which seems to be an indication that it is reacting with the nutrients and minerals already present in the bore water - this doesn't last more than about 3 days.

The good news is that I only use about 300 litres of PH stabilised water for my flood and drain hydro system and about 50 litres for the NFT system. I might need to use another 50L on the NFT during a two week period - I swap the NFT water every two weeks. I sometimes add another 50L also to the Flood and Drain system, which I change every 3 weeks. I use the 'old' water to fertilise my citrus trees and garden.

I've attached a few pictures, which might help as my explanation isn't that concise. :) The first picture is of the flood and drain tank. The second photo is the PH stabilising storage tank. I would also suggest that you get a nutrient mix that doesn't lower or raise the ph too much - many are designed for this. Ask at a hydro store and they should be able to help. Additionally, don't be afraid to experiment a little. I was advised by a hydro store that my bore water would probably not be suitable due to the high CF reading. My NFT has a CF of approx 4 (2.5 from bore water + 1.5 from nutrients) and my flood and drain of about 4.5 (2.5 from bore water+ 2 from nutrients). I had the water tested and have been told that it is fine for drinking...it just has a lot of minerals.:) So far my vegies have tasted great.

Hope this helps

gav

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Hi Gav - in your second photo - what are your plants sitting in - are they suspended in the tubes with mesh baskets - or are they just sitting in the tube - any chance of a close up shot of how the plants are held in the tube? What are you growing?

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Hi Hamish :)

No worries mate, I'll get you a close-up photo tomorrow. The plants are placed straight on to the tube. I have the angle of the NFT on a fall of about 2cm per metre. This allows for the water to gently trickle past the plants' roots system and into the water tank at the bottom. If I have a really small or spindly seedling, I will put masking tape over the hole and poke a whole into it. This gives some support for the first week or so, then it can be removed. It also helps to reduce any algae build-up by keeping the light out.

The mint on the left side of the photo is planted in a pot plant with clay balls. It is suspended over one hole by the 'pot system' that boxsell sell. Basically, a separate spag line is used to drip water into the pot plant and the run-off is collected in the whole and continues down the tube. The mint loves it and it prevents its roots from taking over everything and blocking the tube.

I'm growing heaps of lettuce varieties - nearly everything but iceberg. Soft herbs such as parsley, oregano, rosemary, basil, coriander and thyme all grow well. I use the same nutrient for lettuces and herbs at about 1.5 cf and about 6 - 6.5 ph. I am constructing a new NFT system at the moment and will try to grow toms and cucs at 2.2 cf - it will be interesting to see how it goes.

gav:)

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Thanks for the comments. My reservoir is 12 gallons of liquid, and big enough to hold about 20-30 gallons total.

It seems as though the water likes to return to its original pH before nutrients were added. If I put Mad Farmer Get Down in, the pH will lower, but eventually creep back up, and I have to continually add the Get Down.

6/29 @ 10pm = pH 5.38

6/30 @ 2:15pm = pH 6.10

6/30 @ 8:15pm = pH 6.09

7/1 @ 9:50am = pH 6.29

Also...

I'm wondering if this is the reason to pH balance the water to 6.5 before adding the nutrients?

Lets say your target nutrient level for tomato's is 2200 PPM. If you use hard water that originally had 800 PPM, would you add the two together for a goal of 3000 PPM, or just bring the 800 PPM up to the target of 2200 PPM?

Right now it's not that critical, because I'm using RO water that starts off with very low PPM, but I'm just curious about using tap water.

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Guys I frequently use my electronic pH meter (testing general water, hydroponic & aquaponic water, winemaking/beer making) and I find them to be accurate within 0.2, I am frequently recalibrating and cleaning the electrode so I think that helps, if you are spending less than $100 I wouldn’t recommend it. I am also doing the same with my 2 different types of EC meters (one only displayed in ppm) and find them to be very accurate. I had to recently replace the electrode on one of the EC meters (the one in ppm, the better one too) as I knew it was giving me a false reading and I could taste much more acutely and that alone cost me $80 to replace (just the electrode) so same story applies electronics need good maintenance and need to be reasonably pricy to be any good for long periods of time.

What really matters most in water is the concentration of Sodium Chloride (NaCl) in g/L (of pure NaCl). EC meters test the hardness of water by measuring the amounts of total salts as TDS (Total Dissolved Solids) and can be expressed in ppm, ppt, millisemens and a few others. NaCl is what will have a adverse affect of many plants well before calcium carbonate, magnesium sulphate, magnesium carbonate, iron sulphate just to name a few will cause harm to plants as plants require these compounds to grow in much higher concentrations than that of common salt. An expression of total NaCl g/l is the most accurate way to differentiate between the two. All of these compounds dissolved in water add to the overall concentration (ppm) the more of the compounds desolved in the water the higher the reading. So just remember if you have a high ppm reading it may well not always be a ‘bad’ thing providing it is low in NaCl concentrations, it may be very beneficial in some cases (providing it is not excessively high as this can cause toxicity and stain marks on buildings) for your plants as the plant requires the elements to grow and fruit meaning less fertiliser to apply if at all. Although I will say it is very common to find a high EC reading caused almost solely by NaCl, but you can taste easily the difference between what is what.

On my property I am happy with bore water very high in Epsom Salts (magnesium sulphate) as our soils are relatively deficient in both Mg & Su by which the plants use all I can put on and I still have to apply more of this stuff.

For some reason hydroponics act differently to soil bound plants in general if you were growing soil plants especially beans (and I mean especially beans) readings of 1300 to 1700 ppm would not be very suitable if no technology like magnets were employed (where beans would be almost dead) and others would struggle bar a small few; soils play an important part where sand is most suitable for these getting much worse as the soil moves towards clay. I would say these readings would be well within reason of growing plants hydroponically but, anything over 2000ppm would be pushing it. I have had EC readings of 1500ppm and there has been zero visible setbacks as I’m taking you have also found Gavin. Depending on the NaCl concentrations Gavin I think your tomatoes should be ok go with what looks and tastes right.

Lagreca sorry to be stupid what is RO water?

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I'm sorry for not clarifying. RO is my shorthand for Reverse Osmosis. I have a system at my house to create drinking water, and since my hydroponics system is so small, I can generate enough water for it too.

Here is a link to: 2007 San Diego water quality report

There is also this: Additional Physical, Mineral, and Metal Characteristics report

I am in the Alvarado district. Do those reports show enough to tell if my water is good enough for my hydroponics system?

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Thanks for the info Jonathon. I will get another analysis of my bore water and see what the NaCL levels are - it doesn't cost much up here and it is always fun to see what is in the water. At the moment the vegies taste good.:)

Lagreca...I would think that RO would be okay, seeing most hydroshops tend to suggest using it - Gary and Jonathon can probably help you out with that one a lot better. Regarding your ph readings, I would suggest that you get ph drops as well and use them in conjunction with your metre...at least until you have a base line to work from and they're pretty cheap. I'd do this, just in case it isn't calibrated correctly ie ph4 and ph7 buffer solutions. I had heaps of trouble with mine and eventually found out the ph7 buffer solution was from a bad bunch and was useless.

Depending on what you want to grow though, most plants have a reasonable ph growing range ie Toms can range from 5.2 to 6.7. I would also look at perhaps testing another ph down solution, as 'Mad farmer Get Down' seems to use three different acids..but I can't find what they are.

I've attached a photo of the NFT tubes for you Hamish.

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Thanks for the photo Gav.

I didnt realise Tomatos need pH of 5.2 to 6.7.

My pH is 7.6 - or is it different if in a flood and drain AP system vers a Hydroponic system?

My tomato plants seem ok - but then I dont have anything to compare them to.

What should I look out for if my pH starts to affect them?

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Hi Hamish

I'm not an expert in this mate, but think that there is a about a 1 ph difference between soil and hydro for most plants - the hydro is less. I'm not certain about aquaponics compared to hydroponics.

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Hi Hamish

I'm not an expert in this mate, but think that there is a about a 1 ph difference between soil and hydro for most plants - the hydro is less. I'm not certain about aquaponics compared to hydroponics.

Thanks Gav - hymmmm - ok - can anyone else shine any light on this? Should we be comparing ideal pH for plants to Hydroponics or soil? Why are the hydroponics figures lower than soil? Is it something to do with nutrient lock up in water? If so then perhaps the same woulf be true for AP?

Also - I have just realise this might be a bit off topic - so if Gary or Murray feel like moving me to a new thread called 'pH in Aquaponic vers hydroponics and soil' ill happily move my chat there.

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I have already moved it from "Aquaponic System Discussions" down to this forum area "Intergrated Backyard Food Production"

Intergrated Backyard Food Production is the place to discuss things other than Aquaponics such as Quail, chooks and perhaps Hydroponics and the like as these are all methods of producing food in the backyard.

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Hi Hamish

I'm not an expert in this mate, but think that there is a about a 1 ph difference between soil and hydro for most plants - the hydro is less. I'm not certain about aquaponics compared to hydroponics.

I found this - which is a pH chart for soil grown veges - seems to be the same as the hydroponic list. So I am guessing AP growth will also be best in these same pH ranges.

Anyone want to add their thoughts to this? Seems to be plenty of info on what pH the fish like - and people seem to focus on balancing the pH for the fish and forget about what the plants grow best in.

Seems to me that most veges like pH in the low 6's. Jade perch like pH between 6.5 and 8.5 http://www2.dpi.qld.gov.au/fishweb/14076.html

So it would seem the ideal jade perch AP system would be run at pH of 6.5

Now this brings up another point - water temperature. My jades eat best with temps of 23 degrees C and up. I notice they eat lss in the morning when the temp is around 22. Amazing the difference 1 degree makes to their apetite.

So - how does a temp of 23 or 24 degrees C go with plants in an AP system? Anyone have a chart like the pH chart for ideal temperatures of veges in a hydroponic system? I guess this would be the closest way to compare to AP.

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The temps that the fish like are the same for the veggies. Really, in a AP system you have little choice about the temp that might be ideal for the veggies.. The primary concern is to keep the fish in optimum conditions for them and the veggies will mostly be fine as well.

So the best temp for the fish will be the one to go with if at all possible.

It is not really possible in a home system to be able to rigidly control temp, not without adding much more equipment and cost.

In winter the water has to be heated and there is a fair bit of cost just in doing that in a reasonable way.

Got to be careful that the home grown fish and tomatoes become much too expensive to produce.

In commercial Hydro systems they go to lot of expense trying to keep the water temps right. It is not easy even for a commercial outfit.

That is what I have found to be the case.

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I agree Murray - but it would be good to look at all this and at least know what temps are optimal for plants. The fish are easy - we have this data.

For example - Jades need anywhere from 20 degress C up to grow. I have found they dont eat much at 22 but eat a lot at 23.

If (for arguments sake) the veges I was growing were hapiest at 27 degrees and the Jades also like that temp then I would be looking to design my system to keep the fish and veges happy at 27 degrees. Possibly using evacuated tube solar heating or some other form of heating that does not cost too much to run.

And the reverse in summer which might mean I investigate insulating the tank and grow beds to stop solar heat gain and keep the water cool.

I guess if I can collect all the data on temperature for veges then the decision can be made to heat, insulate or cool the water. In a similar way to getting the pH just right.

If I had know about the pH that veges like being in the early 6's then I would not have added the shell grit which changed the pH to 7.6 (which I thought was optimal for the fish. Didnt even think about the plants - and no one advised me to consider it.

If we can come up with optimum plant and fish pH and temperature then suerly the system will function at its most efficient? If the veges and fish grew even 10% faster or bigger under ideal pH and temp conditions then that makes them less expensive than veges and fish that take longer to grow or are smaller.

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Ok - I found a web site saying ideal hydroponic nutrient temp is 65 to 75 deg F. Which is between 18.3 and 23.8 deg C.

So if the temperature data for hydroponic systems is correct and relevent to AP also - and if the pH range for veges mentioned earlier is correct - then the ideal set up for jades and veges would be temp of 23 degrees (lowest limit for Jades to eat well and highest limit for plant growth) and pH of 6.5 (highest limit for most veges and lowest limit for Jades to be comfortable - although they will tolerate down to 6).

I know this is being pedantic - but I like to know what I am aiming for.

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Here is another site stating that root temps of 24 deg C (75F) or less are best for lettuce. While I would never suggest using a chiller just to bring the temp down for the lettuce - it is interesting to know what is the optimum temp to aim for so we can look at designing systems with apropriate shade, insulation, burying tanks, ventilation, heating (where cost effective) etc... Might also help people choose the appropriate fish for ideal vege growing temperatures. Eg trout may need the water too cold for ideal vege growing...

http://betterbuyhydroponics.com/index.php?pr=Hydroponic_Lettuce_3

Here is a quote that relates to temp.

A water chiller unit of one horsepower is capable of cooling 1000 gallons of solution below 75 F (24 C), which delays bolting of the lettuce and slows the growth of Pythium. In fact, we have found here in the tropics where daytime temperatures exceed 95 F (35 C), it is advantageous to chill the nutrient solution to 65 F (18 C) or slightly less to decrease bolting and Pythium.

Experimental research work by Thompson, H. C. et al. (1998) substantiates reports that root temperatures influence lettuce growth in raft culture. They demonstrated the importance of optimizing root and air temperatures in lettuce production. By using 24 C (75 F) root temperature in hydroponic water culture systems of lettuce the crop growth was maximized under elevated temperatures. This led to the conclusion that lettuce production could be grown in warmer geographic areas.

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Look guys most plants will grow and produce out of their recommended pH range I have seen it with wheat crops many times and still manage to produce quite well. In most cases I have seen plants perform poorly due to lack of water and appropriate nutrients. Although it is not advisable to grow crops outside of there recommended pH range the use of lime is commonly used to apply calcium to the plant rater than increasing pH (it even has said this on my soil tests even if the pH in at the lower end of a plants recommended range). And some varieties of the same plant require different pH levels too.

It is only a small hand full of plants that will grow very poorly outside of there recommended range such as lupins, in general it is not much of a problem, but in hydroponics due to the high cost of everything it is always best to aim for perfect conditions.

Lagreca, I thought that RO means reverse osmosis due to your very low EC levels in your water, I personally don’t like them due to there high purchase cost and continuous running costs as well as the very saline waste product produced that is almost unable to be disposed of economically or environmentally, but they have a place in the world.

In winter the water has to be heated and there is a fair bit of cost just in doing that in a reasonable way.

Got to be careful that the home grown fish and tomatoes become much too expensive to produce.

In commercial Hydro systems they go to lot of expense trying to keep the water temps right. It is not easy even for a commercial outfit.QUOTE]

That is a very valid point that I would agree with 1010% Murray, especially about the cost of production compared to input cost. Another thing I would like to make I saw in another forum about germinating seeds using rockwool; rockwool costs about 50cents/cube and sometimes lettuce on special cost not much more than this in the supermarket so be careful about the input costs you may be losing money, you would be better off raising the seeds in 50% compost to 50% vermiculite in seedling trays.

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Hi,

When a control freak like me starts to get windy about a discussion on control of production parameters it might suggest that we are engaging in too much analysis and too little doing.

Sometimes we have to accept that plants will grow in spite of our efforts rather than because of them.

Gary

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Root zone temps are a real problem in Hydroponics. See the cooling tower manufactured by Boxsell. A 6 mtr tall evaporative tower.

Hamish, you have hit onto another one of the advantages of growing using AP.

Especially using DWC. There is a large water volume employed and water in large volumes is very temp stable, as well as stable in most other ways as well.

In a DWC system we supplied to Mildura a total of 35,000 ltrs of water is in circulation at any given time. During a 10 day 40 deg + heat wave last summer the water temp in the system rose by 1 deg. During this winter the water temp has dropped only 2 deg. No heating or cooling is employed, except for the protection of the system in well constructed grow tunnels and shed.

The farm has recently put in a NFT system running in a separate greenhouse but using water from the AP system as the nutrient source. They are not getting the same results in plant growth in the NFT system. The reason is in most part because of the water temp. Because of the relatively small volume of water passing through the NFT system the water temp coming out of the channels varies greatly from day time to night time in the NFT channels.

Hydro systems, even very large ones employ a relatively small volume of water.

The grower went to NFT because some Hydro expert who does not have a clue about AP convinced the farmer that NFT channel is much cheaper per hole of production than DWC, and that is true....initially for the equipment, but not in the long term for production, and clean production is what it is all about.

You do not get the bonus of a fish dinner from a Hydro system either , :)

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