airstones were a pain in the bung hole 
I dumped them and never looked back.
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Found a cheap titration test kit.
This will give me a way to âmeasureâ and âvalidateâ the results.
That is what I didâŚLOL
What I found was as long as temps are right, you just need the water flowing.
The air stones did not add DO to the mix.
But I kept the air stones for big rootballs.
The air bubbles help to penetrate the thick rootball.
Not a bunch of flow between the roots so DO is probably lower there.
So to summarize here.
I used a DO meter to get in range with a circulation pump only.
Then turned on a large air pump, and checked the DO meter and it was the same or very close.
At that time I knew all the numbers ect, but not now.
The moral to the story is⌠as long as you have enough circulation and proper temps, you do not need an air pump to achieve max DO.
You may need to make sure the center of the root mass has proper DO levels.
I added air stones for that reason, not for DO.
If you can achieve proper DO levels in the middle of a big root mass another way you are golden.
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disolved oxegen cone.pdf (880.4 KB)
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Dissolved Oxygen Levels and Nutrient Temperature
Battle the Pythium Virus in Hydroponics
The essential for consistence in harvests with the utmost quality and yield.
The hydroponic nutrient solution is not just a mix of fertilizer salts and water, there are a number of organisms and compounds commonly found in our hydroponic systems that we need to be aware of. One of the most important of these is dissolved oxygen which is vital for the health and strength of the root system as well as being necessary for nutrient uptake.
Most growers are familiar with the need to have some form of aeration in their nutrient solution - whether they be in a recirculating or a media based system. In NFT systems, this is often accomplished with the use of an air pump or by allowing the nutrient to fall back into the reservoir thus introducing oxygen. However, the effect of temperature of the solution on the dissolved oxygen levels and on root respiration rates also needs to be taken into account. As the temperature of your nutrient solution increases, the ability of that solution to âholdâ dissolved oxygen decreases. For example, the oxygen content of a fully aerated solution at 10C (50 F) is about 13ppm, but as the solution warms up to 20 C (68 F) the ability of the liquid to âholdâ oxygen drops to 9 - 10ppm, by the time the solution has reached 30 C (86 F), then itâs only 7ppm.
While this may not seem like a huge drop in the amount of dissolved oxygen, we have to remember that as the temperature of the root system warms, the rate of respiration of the root tissue also increases and more oxygen is required by the plant. For example, the respiration rate of the roots will double for each 10C rise in temperature up to 30C (86 F). So the situation can develop where the solution temperature increases from 20 - 30C (68 - 86 F) during the day, with a mature crop, then the requirement for oxygen will double while the oxygen carrying capacity of the solution will drop by over 25%. This means that the dissolved oxygen in solution will be much more rapidly depleted and the plants can suffer from oxygen starvation for a period of time.
The symptoms of oxygen starvation which can occur in both NFT and media based systems can be difficult to pick up as they are very general signs. Media based plants are just as prone to oxygen starvation in hydroponic systems as those grown in solution culture, but here we must also take into account the âair filled porosityâ of the media used. This is simply how much air can permeate between the particles in the substrate and selection of a free draining media which wonât break down will ensure that maximum aeration is going to reach the root zone. Injury from low (or no) oxygen in the root zone can take several forms and these will differ in severity between species.
Often the first sign of inadequate oxygen supply to the roots is wilting of the plant during the warmest part of the day when temperature and light levels are highest. Insufficient oxygen reduces the permeability of roots to water and there will be the accumulation of toxins, thus both water and minerals cannot be absorbed in sufficient quantities to support plant growth particularly under stress conditions. This wilting is accompanied by slower rates of photosynthesis and carbohydrate transfer, so that over time, plant growth is reduced and yields will be affected. If oxygen starvation continues, mineral deficiencies will begin to show, roots will die back and plants will become stunted. Under continuing anaerobic conditions, plants produce a stress hormone - ethylene which accumulates in the roots and causes collapse of the root cells. Once root deterioration caused by anaerobic conditions has begun, opportunist pathogens such as Pythium can easily take hold and rapidly destroy the plant.
Another more visible and longer term effect of oxygen starvation which also occurs in waterlogged crops is leaf âepinastyâ. Epinasty is a downward curvature of the plant leaves, resulting in plants which look wilted. If the oxygen starvation continues and is severe, then eventually leaf chlorosis yellowing, premature leaf and flower abscission will occur.
There are a number of things we can do to make sure our nutrient solution is carrying sufficient dissolved oxygen, and this is important when we consider that many of the root diseases encountered in hydroponics have occurred because the root system was damaged in some way, with anaerobic conditions being a major factor in many situations. The first most important factor to remember with oxygen is that the best way to introduce this gas into the nutrient is to have the solution fall back into the reservoir, and the greater the drop height, the better the aeration effect. Breaking the flow up into a fine shower also assists by introducing more air bubbles into the tank. Secondly, while nutrient ppm (EC) does reduce the oxygen carrying capacity of the solution, the effect is very small and temperature has a much greater influence on oxygenation.
Reducing excessive solution temperatures will ensure more oxygen can be held by the solution and the rate of respiration by the roots will be kept down to optimal levels. Thirdly factors such as nutrient flow rate, channel width, length and slope have a large effect on oxygen levels- faster flow rates, greater slopes and shorter channel lengths all assist with prevention of oxygen starvation.
Perhaps one of the commonest problems in hydroponic systems is the Pythium pathogen and what many growers donât realize is that Pythium being an âopportunistâ fungi, often takes advantage of plants which have been stressed by a combination of high temperatures and oxygen starvation in the root zone. Pythium is usually described as a âsecondary infectionâ meaning that the Pythium spores which are actually common in just about all hydroponic systems, donât actually attack the plant until it has been damaged in some way.
Even very clean hydroponic systems and grow rooms which are isolated from the outdoor environment will have some Pythium present as these fungal spores are naturally present everywhere on a world wide scale - in the water, soil, vegetation, carried in the air and in dust, so its difficult to eliminate the source of this disease.
However, one way we can reduce the âspore loadâ is to sterilize any water supply which may be contaminated with high levels of pythium - water from dams, and streams should always be sterilized before use for this reason if Pythium is a problem.
Under the right environmental conditions, virtually every plant species is vulnerable to Pythium, which not only causes âdamping offâ of seedlings but causes root and stem rot of older plants. Symptoms of Pythium on older plants are a wet rot, root systems will be browned, roots hollow and collapsed. Plants may appear to grow poorly, and wilt for no apparent reason - indicating that an examination of the root system is called for. Pythium has an optimum temperature range for infection of plants, this is generally between 20 - 30C (68 - 86 F), although infection can occur outside this range when damaged plant tissue is available for rapid colonization by the pathogen. Low concentrations of Pythium that may not cause problems at lower temperatures will be disastrous at higher temperatures, particularly where the warmer conditions are associated with a lack of oxygen in the root zone and plant stress.
The best preventative measure against Pythium attack is a healthy, rapidly growing plant as this is an opportunist pathogen and will enter at the site of tissue injury or if the plants are overly succulent, weakened or stressed for some reason. Often root damage during the seedling stage as plants are introduced to the hydroponic system is a danger time for Pythium infection. Pythium is of greatest threat during the seed germination and seedling development stage when plants are most vulnerable to attack, and adequate control and elimination of the pathogen during this stage is the best preventative measure of Pythium control in hydroponic systems. Strong healthy plants will develop resistance to Pythium attack during the seedling stage and this will prevent problems at a later stage of growth.
Other preventative measures include the use of a well drained media, thorough disinfecting of all equipment between crops, and control of pathogens during the seedling stages with a suitable fungicide, long before they are introducing into your hydroponic system. Occasionally a very high spore load, combined with excessive temperature will result in Pythium attacking even healthy plants, if this is the case, it is likely that there is an active source of spore production present, and the system must be shut down and disinfected. Sterilization of the water supply with UV light, hydrogen peroxide or ozone , before nutrient are added however, is effective at reducing or eliminating Pythium from the original water supply.
Therefore by ensuring your plants are healthy and stress free, you will not only get the highest growth rates possible, but also prevent problems such as Pythium infection occurring. The variables to remember with regard to the nutrient solution is that aeration is vital to maintain the dissolved oxygen levels, temperatures should be keep within an optimum range, and Pythium is always present, but a healthy plant is the best measure of protection against a disease outbreak. About the oxygen requirement of plants when in flowerâŚits not always the case that plants require more oxygen because they are in flower, a plants oxygen requirement is linked to the size of the root system, temperature and nutrient uptake rates, rather than the presence of flowering.
So since plants such as tomatoes tend to have a rapidly developing root system at the time of flowering, its important to maintain adequate oxygen levels. With tomatoes the requirement of oxygen in the root zone increases gradually up until the time of maximum fruit load and rapid fruit expansion, where the high rates of nutrient uptake increase the oxygen requirement quite dramatically. On the other hand, if oxygen is deficient during flowering, then the flowers and subsequent fruit may drop off as a result, or they may be undersized.
DO testing #1.pdf (44.5 KB)
DO test 2.pdf (42.9 KB)
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Awesome!!!
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heh heh they called it a virus, at the top, but a fungus down below. Itâs really an oomycete(ew-my-seat).
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Whatâs the stainless nut with a âTâ youâre talking about? Can you take a picture or describe what that is and does?
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Itâs an airline T with a stainless nut for weight. MAke sure itâs high grade stainless not the junky rusty kind.
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How long have you been running dwc like this? I have a whole bunch of plastic tees and nuts i can find easily.
Soon I plan to run a 31 gal bin with 4 air lines, 1 per foot. Iâll have to see the tees. Any chance you can do a video of the bubbles?
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Probably been at least 16 years Iâve been using the Tâs. Might even be 20 years lol! I learned that trick from the original OG 1.0
Iâll post a video of it in a bit on my youtube channel.
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Whatâs OG 1.0? Can you link me to your youtube channel? I want to see what other tricks you have 
Oh sweet summer child.
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OG 1.0 was the original overgrow. youtube.com/@hashmatty Iâll go get the footage now.
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yes, Dr Lynette Morgan is a very respected author and hydroponics expert.
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Holy crap, I canât even believe you said that. She is literally my hydroponics Goddess.