Since you have more volume in your fish tank then you have in your grow bed then you need to think of it of how many fish can my grow bed support... and also how many fish do I need/want to eat as opposed to just having the fish for plant growth. If you want to grow fish to eat (more fish) then you will need more grow beds for more filtration. If you just want you plants to do great then you only need to be feeding your fish 15 - 20 grams of food per square meter of growbed per day. So not many fish. 10-20 goldfish would do it.
Thanks for the feedback!