Marine block / spheres

[Eddieg]

Hi.
is it best to put marine block /spheres or cheato int my refugium.
Regards
Eddie

 

[Ludders]

They primarily do different things. Your bio spheres or blocks increase the surface area your AOB and NOB can live off. People use them as a substitute to masses of rock or sand to make up the shorfal of your biological filtration.
Chaeto will consume your phosphates and nitrates, but it's all a fine balance.