I am not opposed to it - I asked the folks at speciality store if it was necessary and they said no so I never bought one. I am still new to this hobby. Can I just buy one from specialty store and put it in? Will it throw off any parameters or shock the fish?I just think you’re not helping the situation by not using what nature needs for thriving. A tetra filter is for freshwater, not saltwater, and even less for a reef tank.
You need biodiversity and micro organisms won’t be living in that tetra filter.
You have room in your tank for dry rock. In a few months, it will become live rock. Why not go this way ?