I grow in coco also and have had "off" odors coming from my grow. I never removed the plant from the pot to look at the roots so I dont know if they were brown or not. I was afraid it might be root rot so I searched around and read about using pool shock in the reservoir. I found this thread about how to use it, made some and added to my rez and in just a couple days everything smelled good again. The thread is 11 pages long but worth reading.
That is correct. Same EXACT ingredient as EZ Clone Clear Rez that sells for $20 a QT. Get your self a 1 lb bag of HTH Pool shock non PH buffered available online and most hardware stores (bought mine from Ace). Mix 1 GRAM (450 in the bag) per gallon of solution. Will make the SAME EXACT...
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Good luck with your grow.
Edited to add: I wrote this down on my bag. I bought the pool shock at Ace Hardware. It was the 56.44% stuff. A lot of posts dont say which percentage they use. It comes in different strengths. Just an amount that they add. I found a thread somewhere (don't remember where) that had all the math to work out the exact amount. This is what I wrote on my bag of HTH Pool Shock:
1gram/gallon water then 1oz of that mixture per 5gal (rez) or
.3 grams/gal per 10 gal (rez) = 3ppm (for this I just mixed the .3g in a small amount of water and dumped it in the rez)
I've read 1-5 ppm is safe. I went middle road.
I've used the 1g/gal then 1oz per 5 gal rez water for my indoor grows many times with no injury to my plants. It cleared up the off odors and I could actually smell a little bleach odor but clean smelling.
I have some hot peppers growing outside in a recirculating hydro setup and I just did the .3g/10gal this morning. The rez was looking a little dirty.
Hope that helps.