Backyard Aquaponics
A place to discuss aquaponics

I am starting my first system and am looking to make it rather large. I have heard about IBCs and live in a farming region so these would be easily obtainable. I would prefer to use a larger tank for my fish, around 4-500g but am wondering which plastics are the safest for my fish. A little help?

It's not just the fish you need to worry about, it is yourself as well. So you actually have a more limited range than just "fish safe" plastics, you should ideally go for "food grade" plastic, or products deemed safe for "potable water".

That said....many people run systems with only fish safe products and survive just fine....so far

High density polyethylene (HDPE) is one of the most common food grade plastics available. Many of the poly tanks designed to hold drink water for humans (potable water) will be made of this. Stock tanks may or may not be made of this.

Square tanks are difficult to get to swirl and so it is hard to get the fish waste out

yes, square tanks can cause some problems, but if you oversize your pump a little and divert flow back into the tank at stategic points, you can pretty easily "push" your solids to one area for your slow or pump to pick up