Here's some info from Heath about D.O :
"In this you can see that at 19 deg C its about 9mg / L of DO, so not quite 1 mg for every C the temps are raised but a useful rule of thumb. this is sufficient for healthy plant growth, the optimum for nutrient temps is between 18 and 24c
As growers we are caught in a "catch 22" situation because DO is increased at low nutrient temps but the plant growth is regulated by performing countless numbers of biochemical reactions which will double for every increase of 10 degrees C degrees or on the other hand be cut in half for every reduction of 10 degrees C, so there is the dilemma...... which leads me on to some possible answers
The recirculating systems I use all rely on one simple fact and that is whenever air is in contact with the water, whether through natural or artificial means, a transfer of oxygen from the air to the water takes place at the surface which provides a good gas exchange allowing oxygen to enter the water and carbon dioxide to escape until the water becomes saturated. The speed at which oxygen from the air enters and mixes through a system depends on the amount of agitation at the water surface, the depth of the system and the rate at which it mixes itself.
When normal airstones are used most of the DO is obtained when the bubble forms and then by water movement at the surface, so most of the DO is created by water movement at the surface rather than bubbles as most people think. Another thing growers should consider is the practice of placing a large airstone underneath the roots and allowing it to bubble away furiously can cause mechanical damage to the roots and the turbulence can cause stress. Much better to have the bubbles generated in a remote rez and recirculate them through the system.
Ceramic Micro air Diffusers (CMD) are brilliant for aerating your system, if you have never seen one running you are in for a treat, when you first run one its a surprise to see what looks like milk streaming out of the diffuser! or a bit like underwater fog, with one of these you can oversaturate depending on the size of the diffuser or system but not to the point that the system is toxic. If you decide to use one of these, depending on how good the CMD is you can run them intermittently as the DO will stay in the system for about 20 mins .
I wouldn't recommend the use of CMD with oxygen as you would run the real risk of it becoming toxic but not at the levels you suggest it would have to be more than double 14mg DO / L."
"In this you can see that at 19 deg C its about 9mg / L of DO, so not quite 1 mg for every C the temps are raised but a useful rule of thumb. this is sufficient for healthy plant growth, the optimum for nutrient temps is between 18 and 24c
As growers we are caught in a "catch 22" situation because DO is increased at low nutrient temps but the plant growth is regulated by performing countless numbers of biochemical reactions which will double for every increase of 10 degrees C degrees or on the other hand be cut in half for every reduction of 10 degrees C, so there is the dilemma...... which leads me on to some possible answers
The recirculating systems I use all rely on one simple fact and that is whenever air is in contact with the water, whether through natural or artificial means, a transfer of oxygen from the air to the water takes place at the surface which provides a good gas exchange allowing oxygen to enter the water and carbon dioxide to escape until the water becomes saturated. The speed at which oxygen from the air enters and mixes through a system depends on the amount of agitation at the water surface, the depth of the system and the rate at which it mixes itself.
When normal airstones are used most of the DO is obtained when the bubble forms and then by water movement at the surface, so most of the DO is created by water movement at the surface rather than bubbles as most people think. Another thing growers should consider is the practice of placing a large airstone underneath the roots and allowing it to bubble away furiously can cause mechanical damage to the roots and the turbulence can cause stress. Much better to have the bubbles generated in a remote rez and recirculate them through the system.
Ceramic Micro air Diffusers (CMD) are brilliant for aerating your system, if you have never seen one running you are in for a treat, when you first run one its a surprise to see what looks like milk streaming out of the diffuser! or a bit like underwater fog, with one of these you can oversaturate depending on the size of the diffuser or system but not to the point that the system is toxic. If you decide to use one of these, depending on how good the CMD is you can run them intermittently as the DO will stay in the system for about 20 mins .
I wouldn't recommend the use of CMD with oxygen as you would run the real risk of it becoming toxic but not at the levels you suggest it would have to be more than double 14mg DO / L."
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