I must add as well that you are buying dead fish swimming. Your ammonia level will spike for two weeks. You will need to do 75% water changes daily. This will do much damage to your fish, Then nitrites will spike, and you will need to do 75% water changes daily for another three weeks, and even more damage will be done to your remaining fish. You are going into this way too gung ho. Send me a PM in a month, and I will ship you some Tilapia to replace your first batch. I am not joking. Without established biofiltration, your fish are going to poison themselves. Wait! Get the filter cycled, and order some fish at that point. There are plenty of online distributors. Tilapia are crap machines. I have kept lots of fish in big tanks, and I have seen few fish put out this much waste. Your system needs to be eating close to 10 ppm ammonia per 24 hours before you put that amount of fish in it.
Edit. Saw your gallonage, and density, and it may not be quite so bleak. At least get a test kit, and be prepared for massive water changes.
