I think you would get a better response if you asked this in a hydroponics forum. Hydroponics and organics don't seem to have much in common.

Rockwool is a spun mineral product and is used in hydroponics, but as Dave stated hydroponics and organic gardening are not compatible since hydroponics relies so much on synthetic plant foods.

Way back when I tried to get a guy interested in organic hydroponics using dissolved organic fertilizers like milk, seaweed, and blood meal. He asked how to disinfect the mold and mildew that normally grows on his pipes and the conversation went downhill from there.

hi kimmsr & dchall_san_antonio,

You both are right about rockwool, but many experts
suggest compost tea with seaweed, afalfa, molases and
other organic substances, using rockwool.

Has anyone experience in hydroponics with compost tea
as the only nutrient supplier ?

Sapam99

If there is anyone out there successfully growing plants hydroponically with just compost tea they are being very quiet about it. I have not heard of anyone doing that, sucessfully.

In the traditional hydroponics implementation, I would be surprised if compost tea would support plants. Compost tea is better at providing microbes than it is at providing plant food. Hydroponics is about feeding the plant, not the soil. Compost tea "feeds" the soil by providing microbes which, in turn (3 weeks later), feed the plants. Natural plant food comes as a result of a healthy soil food web. By the definition of hydroponics, the soil food web is absent.

Just groping here but I would suggest, if on is really interested in elementary hydroponics using naturally available stuff you might want to look into efforts in India about half century ago. Big university libraries had periodicals with articles on such things back then.

Aquaponics is organic.
The OP is asking the right group to find what is not harmful to he/she. Is not that what organic gardening are all about?