DOHOAquarium Filter Media Bio Ceramic Brick Bio Balls for Fish Tank 2 Pcs

I can only assume that this is doing what it claims as far as housing my beneficial bacteria. I've had it in my reef tanks sump for about 6 months and it's still intact and I have not had any ill effects from having added it.

These are very solid and sturdy, but in a good way. They are very porous, but they are not brittle. They keep their shape, and they don’t crumble. I like how flat they really are. I stacked them up and use them as a way to lift the skimmer up in my sump as well. Makes a great stand, and it’s functional as well. Would recommend and buy again.

Seems to be working alright

Using these blocks to hold my protein skimmer up higher, while adding biological filtration. Really well built.

Great product. I love it! Best media