Pretty sure I've read posts about it and here is what cc sent me....no more than 15-20% cut, will stimulate lateral growth, here it is
Root Pruning To Aid in Proper System Function
When growing in any water culture system, its important to keep your root system as healthy and well maintained as possible. Aside from the typical means of promoting root health such as solution aeration, balanced water chemistry and proper water temps, there are other things to keep in mind.
One important element in keeping a functional, yet maintained root system is root pruning. As your plants proliferate it’s fairly common for the root systems to begin heavily populating the growth module and in some cases the circulation conduit. Here are a few simple tips to help avoid this from becoming an issue and hindering the circulatory function of the system.
1) Once plants are introduced into the system, monitor root growth to be certain roots are developing well. While examining keep an eye out for roots that tend to be growing longer than the rest of the root mass. Simply prune these “runner” roots with a clean pair of scissors to help maintain a more compact and uniform root mass. This pruning will also promote the proliferation of more lateral root growth which will aid in your plants developing a healthy root mass.
2) Occasionally repeat the examination process to ensure roots are developing well. Root prune as need be applying the same method as above. If necessary, reach down into module (thru port hole in lid) and pull out any runner roots that may be growing into the return manifolds. Keeping this return manifold clear with provide for better function of your UC.
3) Avoid the use of supplements that aid in root proliferation beyond the vegative cycle. Plants will continue producing roots throughout the bloom cycle naturally. Use of these supplements into bloom can cause unnecessary energy to be put into root growth and focused away from flowering.
Root pruning rule of thumb: Be certain to not ever prune more than 15-20% of your root mass at any one time to maintain optimum plant health. Always prune the most anterior (outter) points of the root mass and use sterilized tools to avoid infecting plants with pathogens.
