Thick, fat, white furry roots are what you most want to see in Hydro- they are absolutely indicative of healthy root growth. Be aware however that the color of a nutrient solution will stain the roots, turning them yellow or brown. This is also true of many nutrient additives. Older, more mature plants will have a darker cream-colored root system, and some plants just tend to have a natural cream colored color pigment. Those Stealth Hydro pre-packaged nutes always leave the roots WHITE. The Grow Nutes leave a slight Green tint and the Bloom Nutes leave a slight pink tint.
Root Zone Temperature
The temperature of the root zone and the temperature of the nutrient water solution can have a major effect on the healthy growth and appearance of the root system. In general the temperature should be between 68 and 72 degrees farenheit. Anywhere between 64 and 74 will be OK. Colder or warmer conditions can cause poor and stunted root growth, as the roots don't want to grow into the unhospitable nutrient solution. Major root death can occur in even brief periods of cold or heat stress. Poor temperature conditions leave the door open to root disease.
Some would argue that one of the strengths of hydroponics is its sterile environment, and the notion of exposing growing systems to bacterial and fungal organisms would be self-defeating, if not sacrilegious. These growers rely on sterile growing environments, strong disinfectants and a product like SM-90.
Another option is Hydrogen Peroxide. Each of these offer their own protection and benefits. But NEITHER SM-90 or Hydrogen Peroxide works well with organic nutes or organic additives in the reservoir. You can not try to kill the organic algae or pythium and add organic materials back. That just won't work!
They do not work well together and SM-90 has also been known to react poorly with Superthrive.In a sterile growing environment, your goal is to have a super clean reservoir. This is harder than it sounds. Folks who have been growing in the same area with the same equipment for years might find that they are suddenly having root problems when they never had them before. Or a new grower might begin having problems right from the beginning because of his water or temps.
Keeping your reservoir totally sterile can work very well, but once you get a population of icky badness it will keep coming back again and again. Some pathogens such as pythium are almost impossible to get rid of completely. No matter how many times you sterilize everything with a bleach solution, the problem returns. It can get very frustrating and expensive to constanly be battling. More and more innovative growers are moving toward a more wholistic approach of using good microbes in the reservoir with organic nutes or staying with strickly chemical nutes..
One option is to use no organic additives at all and to rely strictly on chemical nutrients based on fertilizer salts. We think a better choice is to continue using organic material, but also using an enzymatic addtive like Hygrozyme that will break down the unwanted organic matter in the reservoir . If you would like to use additives such as bat guano, compost or fish-based products, you might consider run to waste instead of a recirculating system.
I have to add that the above mentioned additives other than Peroxide can really screw with your pH.
Look at the PEROXIDE STICKY on this forum for more info