So i decided to give it a try.
I used small pebbles in this experiment, the pebbles were about 5 mm in size. easy to handle and the system started to grow well.
Well as a lot of experts from various online forums did mention that this will not work.
And after a few months, tomatoes were happily growing until one day i noticed that the water flow was not the way i would have liked it to be.
This is precisely 5 months after i started the system and the problem started.
Root clogging, had caused the problem .. the roots were really big and used up all the space between the small pebbles and there was no space for the water to flow. Also the flood and drain did stop working and this adds to the supply of oxygen the to roots to be cut off.
This is a little expensive material and one ca use 20 - 25 mm gravel or river pebbles as well.
Gravel or river pebbles are a lot heavier compared to the LECA, so having a large system on your roof top with gravel or river pebbles will be a bit challenging.