7 fish won't produce enough poop to do, excuse the expression, shit. With 7 fish you don't need a clarifier or anything else unless these folks are WAY overfeeding. The system has way too little growbed for a real system. Looks to me like this is a hydroponic system in aquaponics clothing.

If you want to use a raft system you must remove the solids. That is incredibly wasteful. Put the solids through gravel growbeds with red worms fill & drain. What comes out you can use in a raft system.

In a 100 gallon system you need about 50 fish to provide the nutirented needed for a good growth of plants. That is not to say some greensand or blood meal is needed to suppliment iron, but it is a good start.