Algae Turf Scrubbers (ATS) are becoming all the rage lately and are a highly efficient way to export nutrients from your system. For their size, they can export a considerable amount of nutrients and are great for a small space.
But do you still need to use Granular Ferric Oxide (GFO) with an ATS? Well, it depends.. they are both exporting phosphates and could potentially compete against each other. If your running an ATS iI would avoid using GFO unless your algae turf scrubber can’t keep up with your phosphate export requirements. The simple fix is to just put less food into the tank but if your fish need some fattening up then it may be worth either getting a bigger ATS or supplementing with a small amount of GFO (careful not to use too much!)
The advantage of an ATS over GFO is that its a chemical free export method that can also remove nitrate and harbor pods whereas GFO is targeted at Phosphate only.. That and there is no media to buy and replace.
The advantage using GFO over ATS is GFO is highly efficient at removing phosphates with a small reactor. You have to be careful not to run too much gfo as it could strip your tank too clean and harm your corals.