PPM or Testing Nutrient Levels w/ a meter

[Michelle Silva]

I just realized that when I tested ppm with a meter it was a borrowed meter from someone who grows hydroponically and that the levels in an organic (AP) system may not read accurately. I've never researched PPM levels,and it doesn't really matter to me as long as things are growing.

I did have blossom drop on some, the flowers never produced..I believe it was the ones that were all part of the same family (squashes, cucumbers etc).  I had tested with the meter out of curiousity.

Does anyone have any experience with using meters to test ppm in an AP system or is it not possible? 

[TCLynx]

a meter that is used to for testing the nutrient levels in Hydroponics won't give you a meaningful number for aquaponics.  See the TDS or EC or other meters for Hydroponics actually read the conductivity of the water which is mostly related to salt content in the water.  This is because most of the hydroponic nutrients are mineral salts and therefor can be roughly estimated by the use of a conductivity meter (of course the meter can't really tell you which nutrient is at which level and since they will get out of balance over time, that is why hydroponic nutrient needs to be dumped and replaced regularly.) 

Anyway, about the only use I've found for my bluelab truncheon left over from my hydroponic days is to very roughly (and probably a bit inaccurately) estimate the salt levels in my system if I think I need to salt for fish health. 

 

So, since aquaponics is not using mineral salts to provide the nutrients to the plants, do not try to use a ppm meter and hydroponic guidelines about nutrient strength to figure anything out about aquaponic nutrient levels, it will be meaningless (would be sort of like measuring the salt levels in a cake to figure out if you have enough sugar in the recipe.) 

The more appropriate way to measure nutrients in the Aquaponic system would be the Nitrate test or if you want to get really into testing you could pick up tests for phosphorus and potassium as well as others but I wouldn't know what levels you need to aim for nor how to adjust them.  Generally, if you have a measurable amount of Nitrate, you probably have enough nutrients though adding some maxicrop can help with potassium and trace elements occasionally and some people find they need to add iron too.

[Michelle Silva]

Thanks for the info!

TCLynx said:

a meter that is used to for testing the nutrient levels in Hydroponics won't give you a meaningful number for aquaponics.  See the TDS or EC or other meters for Hydroponics actually read the conductivity of the water which is mostly related to salt content in the water.  This is because most of the hydroponic nutrients are mineral salts and therefor can be roughly estimated by the use of a conductivity meter (of course the meter can't really tell you which nutrient is at which level and since they will get out of balance over time, that is why hydroponic nutrient needs to be dumped and replaced regularly.) 

Anyway, about the only use I've found for my bluelab truncheon left over from my hydroponic days is to very roughly (and probably a bit inaccurately) estimate the salt levels in my system if I think I need to salt for fish health. 

 

So, since aquaponics is not using mineral salts to provide the nutrients to the plants, do not try to use a ppm meter and hydroponic guidelines about nutrient strength to figure anything out about aquaponic nutrient levels, it will be meaningless (would be sort of like measuring the salt levels in a cake to figure out if you have enough sugar in the recipe.) 

The more appropriate way to measure nutrients in the Aquaponic system would be the Nitrate test or if you want to get really into testing you could pick up tests for phosphorus and potassium as well as others but I wouldn't know what levels you need to aim for nor how to adjust them.  Generally, if you have a measurable amount of Nitrate, you probably have enough nutrients though adding some maxicrop can help with potassium and trace elements occasionally and some people find they need to add iron too.

[TCLynx]

Hope it helps