So I bought an all in one 20g and it came with a bio-wheel. I’ve heard these are pretty bad for a reef tank, so I took it out, and replaced it with some matrix media. Is this okay?
The tank should have rock, rock is the biofilter on a salt tank. You can add extra media if you want, but it does not provide ‘extra’ biofiltration. The only real benefit to the extra media is if you want to transfer over the bacteria to another tank, like a hospital tank for the example. Google ‘the Berlin method’ for more explanation of how the rock provides biofiltration.