I lied.
Instead, I bought Dr Tim’s Waste Away: $30 for 1 pt. Liquid at the LFS. He raises corals and saltwater fish and recommended this as it is what he uses.
It says that it is specifically for saltwater tanks so I figured it would work fine in the brackish tank. I put a half dose in all my tanks, and the freshwater tanks seem to be clearing up immediately. The brackish tank doesn’t look any different yet.
My water was already very clean, & I expected the water to initially get cloudy in these tanks. Instead, it got even clearer, within 2 hours.
I was going to siphon the brackish tank today, but instead I’m going to stir the bottom and give it a second 1/2 dose.