I actually got the tank and filter system for free from the side of the road. The stand was trash and the tank is starting to separate at the top in the back. I supported that with wood all the way around my stand, not sure it will work but it has been doing well so far. The tank has both red lava rock that I assume will add iron (total assumption, never confirmed with any sort of scientific mind) and the rest is either PVC matrix to push fish poop into the sump, or aquarium gravel. The gravel gets really expensive when you need 100 pounds to cover the bottom. I don't think the gravel is necessary but I like the aesthetics. The only work I did on the tank or sump was drilling the holes for the Uniseals and the 1" PVC for water flow between the two reservoirs.
Right now I have the one Silver AK plant, thought the system was supporting 5 plants, 3 of which were the size that the last one is now. All of the nutrients are provided by either frozen blood worms or API Pond Pond Fish Food (that is the exact name, in a 1.56kg tub). There were 20 comet goldfish when I started, the cheapest ones I could find, thought I think I'm down to something like 15 from trying different aquaponic setups and having some nutrient overloads kill some of the early attempts. Those were all the small systems. Once I moved to the garage and got the big system setup, with 1.5 hours of water every 3 hours this system has been flawless. I have spent more time watching the fish and clipping the leaves than anything else.I checked the aquarium nutrient levels 3-4 times in the first week and they never rise even close to danger areas for fish.
If I hadn't gotten the tank I would have used an IBC container.