The airstone gives the nutes oxygen and keeps the nutes from setteling on the bottom .
Now , you can fit four 6x6 Rockwool blocks in your setup. Some people like to use Hydroton on the bottom of the tray but for me , this just adds more expense. Some people will also put rockwool slabs in the bottom . This will help give the roots more room to expand , but for the room you have ...this is not necessary. I like to use the blocks by themselves and just set the in the tray all by themselves. The root system will grow in block and is plenty of room to grow a plant to above 4 feet. I bet that with this method and four plants , you will yield about 10 to 12 ounces your first grow.
Now , you can fit four 6x6 Rockwool blocks in your setup. Some people like to use Hydroton on the bottom of the tray but for me , this just adds more expense. Some people will also put rockwool slabs in the bottom . This will help give the roots more room to expand , but for the room you have ...this is not necessary. I like to use the blocks by themselves and just set the in the tray all by themselves. The root system will grow in block and is plenty of room to grow a plant to above 4 feet. I bet that with this method and four plants , you will yield about 10 to 12 ounces your first grow.