Like Cecil said with respect to the ammonia. you will have ammonia problems. Frequent water changes prolong the time needed to "cycle" your BOW's. This is all moot now since you have fish swimming.
I don't know about the goldfish, but the tilapia will do fairly well with once cycled with occasional water changes and zero filtration IF you allow the algae to flourish....You will have a "green water" system. Your algae will become both food and bio-filtration. HEAVY aeration is required for this to keep the fish waste in suspension and degrading rapidly. Tilapia will generally top out at 3/4 pounds if allowed to spawn with this system.
There is NO question using a quality bio-filter and something to remove solid wastes will vastly increase water quality, stocking density, growth rates....everything.
