On rare occasions, "black" ick forms in the BioSphere. There are few types of black ick including invasive bacteria (most common) and black algae (very rare). While it will not harm the frogs, it will harm the bacteria that sustain the BioSphere. This will lead to the breakdown of the BioSphere and a toxic environment for your frogs.
We all want a safe and healthy environment for your frogs, so our recommendation is to replace the BioSphere.