Extreme indoor FUNGAL problem
I am trying to identify a long-term and insidious fungal disease that I have been battling for over ten years. This disease manifests itself in the root zone and tank and seems to largely affect plants in early stages of growth, while seeming to disappear as a plant matures. Apart from fouling the nutrient tank and slowing growth, this pathogen is fairly invisible. I have gone to extreme measures to clean and disinfect the room and equipment, including change of equipment to no avail. It reappears every crop. Over the years, treatments have included combinations of fastidious cleaning, microbes, systemic fungal treatments, root zone cleaners, etc. With persistence, plants eventually seem to recover and grow normally...until the next crop!
Outside United States
The first step to managing this problem is to properly identify what the problem is. It's hard to tell what the exact problem is. Do you have access to a plant diagnostic clinic? They can examine a sample of the affected plants and be able to identify the organism involved. Once you know the exact problem you will be able to properly target and manage it.
It sounds like you are growing in a hydroponic system? If so, keep in mind that there is a period of time when the plants are first getting established that the nutrient solution can develop a flush of microorganisms (bacteria, fungi, etc.) that looks white, cloudy, slimy, etc. How are you starting the plants that you add to the hydroponic system? If there is any organic matter (bits of growing media, etc.) these can serve as a food source for the microorganisms. Also make sure to closely monitor the nutrient solution pH and adjust as needed. A swing in pH can also contribute to microorganism overgrowth in the nutrient solution. Some nutrient solutions themselves can contribute to the problem if they are soil based.
Hope this helps and thanks for using Ask An Expert!